California's emergency declaration reflects the evolving threat posed by H5N1 avian flu. No single event indicates that a pandemic is imminent, but taken as a whole, the changes warrant greater attention from enterprise business. PHC recommends that business continuity plans be reviewed and updated in preparation for high consequence infectious disease threats.

California declared a state of emergency to manage the ongoing H5N1 threat. The emergency declaration allows for flexibility to adapt to the shifting situation as the threat evolves. [Confidence: Very High]

This 1st severe case of H5N1 avian influenza warrants greater attention from enterprise businesses. No human-to-human spread of H5N1 has been detected, but identification of the first severe case coupled with continued identification of known or probable human novel influenza cases without a known exposure raises the likelihood that the virus is evolving and undetected spread could be occurring. Businesses should follow the recommendations provided in the PHC analysis on October 22, including ensuring the business continuity plan addresses high consequence infectious diseases and lowering barriers to seasonal flu vaccines for their employees.

Update to the human H5N1 avian influenza case in Louisiana (see PHC alert 12/16): the case has been hospitalized, making this the first case of severe H5N1 illness in the US. The case's virus belongs to the D1.1 genotype related to other D1.1 viruses recently detected in US poultry and in recent human cases in British Columbia, Canada, and WA state. This is different from the B3.13 genotype detected in dairy cows, sporadic human cases in multiple states, and some US poultry outbreaks. [Confidence: Very High]

California's proactive testing is expected to detect additional H5N1 cases in dairy herds. No human-to-human spread of H5N1 has been identified. Businesses should follow the recommendations provided in the PHC analysis on October 22, including lowering barriers to seasonal flu vaccines for their employees. The CDC is offering free seasonal influenza vaccines to farmworkers in high-risk states.

California has detected H5N1 avian influenza in 7 additional dairy herds, half of the state's dairy herds (645 affected). See PHC alerts from 12/16, 12/12, 12/6, 11/22, and 11/21 for info about earlier totals. [Confidence: Very High]

This probable H5 avian influenza case does not change PHC's recommendations for businesses. No human-to-human spread of H5N1 has been detected, but continued identification of known or probable human novel influenza cases without a known exposure raises the likelihood that undetected spread could be occurring. Businesses should follow the recommendations provided in the PHC analysis on October 22, including lowering barriers to seasonal flu vaccines for their employees.

Delaware identified a possible case of H5 avian influenza during routine surveillance. The CDC tested a sample, but could not confirm influenza A. The CDC listed the individual as a probable H5 case, the 7th probable case. The individual has no known exposure. [Confidence: Very High]

California's proactive testing is expected to detect additional H5N1 cases in dairy herds. No human-to-human spread of H5N1 has been identified. Businesses should follow the recommendations provided in the PHC analysis on October 22, including lowering barriers to seasonal flu vaccines for their employees. The CDC is offering free seasonal influenza vaccines to farmworkers in high-risk states.

California has detected H5N1 avian influenza in additional dairy herds, now half of the state's dairy herds (630 affected). See PHC alerts from 12/12, 12/6, 11/22, 11/21, and 11/15 for information about earlier totals. [Confidence: Very High]

Given California's proactive testing, the detection of an additional H5N1 case in a dairy worker is not unexpected. Businesses should follow the recommendations provided in the PHC analysis on October 22, including lowering barriers to seasonal flu vaccines for their employees. The CDC is offering free seasonal influenza vaccines to farmworkers in high-risk states.

California reported 2 new cases of H5N1 avian influenza in dairy workers, totaling 34 H5N1 cases in the state this year (33 dairy industry-related cases and 1 with unknown exposure). No human-to-human spread of H5N1 has been detected. [Confidence: Very High]

The identification of 2 fatal suspected H5N1 infections in cats that consumed raw milk underscores the potential risks of raw milk. Raw milk should not be consumed. Pasteurization inactivates H5N1, making pasteurized milk and milk products safe to consume. Businesses should follow the recommendations provided in the PHC analysis on October 22, including lowering barriers to seasonal flu vaccines for their employees.

The Los Angeles County Department of Public Health is investigating two possible cases of H5 bird flu in cats that consumed recalled raw milk. These fatal cases tested positive for Influenza A (a group of influenza viruses that includes H5N1), an uncommon finding in cats. Cats dying has been frequently observed on dairy farms with H5N1 outbreaks. Raw milk presents serious health risks to people and cats. [Confidence: Very High]

California's proactive testing is expected to detect additional H5N1 cases in dairy herds. No human-to-human spread of H5N1 has been identified. Businesses should follow the recommendations provided in the PHC analysis on October 22, including lowering barriers to seasonal flu vaccines for their employees. The CDC is offering free seasonal influenza vaccines to farmworkers in high-risk states.

California has detected H5N1 avian influenza in 32 additional dairy herds, totaling 559 and approaching half of the state's dairy herds. See PHC alerts from 12/6, 11/22, 11/21, and 11/15 for information about earlier totals. [Confidence: Very High]

This update does not change PHC's recommendations for businesses. No human-to-human spread of H5N1 has been detected. Businesses should follow the recommendations provided in the PHC analysis on October 22, including lowering barriers to seasonal flu vaccines for their employees. Raw milk should not be consumed. Pasteurization inactivates H5N1, making pasteurized milk and milk products safe to consume.

Update to suspected avian flu case in Marin County, CA (see PHC alert 12/9): officials reported that the suspect case became ill after drinking raw milk. An investigation is underway to see if there is a link between consumption of raw milk and the child's illness. There is no evidence of person to person transmission. [Confidence: Very High]

This update does not change PHC's recommendations for businesses. No human-to-human spread of H5N1 has been detected. Businesses should follow the recommendations provided in the PHC analysis on October 22, including lowering barriers to seasonal flu vaccines for their employees.

CDC confirmed that the strain involved in the Alameda County, California pediatric avian flu case is similar to the H5N1 strain circulating in dairy cows and poultry, though they could not definitively identify the exact genotype. Officials were unable to find an exposure source. See PHC alert 11/19 for earlier info about this case. [Confidence: Very High]

Evidence of additional dairy herds infected with H5N1 is not surprising. Businesses should follow the recommendations provided in the PHC analysis on October 22, including lowering barriers to seasonal flu vaccines for their employees. The CDC is offering free seasonal flu vaccine to farmworkers in high-risk states. Pasteurization inactivates H5N1, making pasteurized milk and milk products safe to consume. Raw milk is illegal in Nevada.

Nevada is the 15th state to report evidence of H5N1 avian influenza in dairy cattle. The affected herd is in Nye County. Confirmatory testing is underway. No human cases have been reported in this event. [Confidence: Very High]

Given the wide media coverage around this study, businesses may receive questions regarding this case. The scenario presented in the paper doesn't mean imminent human-to-human transmission is certain, but it highlights the virus's potential adaptability. This study does not change PHC's recommendations. Businesses should follow the guidance provided in the PHC analysis on October 22, including lowering barriers to seasonal flu vaccines for their employees.

Researchers reported that H5N1 could be "one mutation away" from becoming highly transmissible among humans. Influenza viruses mutate every year, but a specific genetic modification would be required to enable more efficient human-to-human transmission. [Confidence: Very High]

For information only. The establishment of broader milk testing and information collection will clarify the extent of H5N1 infection in dairy cattle nationally. Businesses should follow the recommendations provided in the PHC analysis on October 22, including lowering barriers to seasonal flu vaccines for their employees.

As part of its National Milk Testing Strategy, USDA issued a new Federal Order requiring that raw milk samples nationwide be collected and shared with USDA for testing upon request. The order also requires herd owners with positive cattle provide information that supports contact tracing and disease surveillance. [Confidence: Very High]

Businesses and individuals should dispose of any affected products. H5N1 avian flu and other pathogens have been found in raw milk. Pasteurization inactivates H5N1, making pasteurized milk and milk products safe to consume.

California has again expanded the recall of raw milk-related items from Raw Farm of Fresno County. Raw Farm milk products have tested positive for avian influenza at retail and dairy storage and bottling sites. The affected lot numbers are 20241109 through 20241127. No illnesses have been identified tied to the contaminated product. [Confidence: Very High]

California's proactive testing is expected to detect additional H5N1 cases in dairy herds. No human-to-human spread of H5N1 has been identified. Businesses should follow the recommendations provided in the PHC analysis on October 22, including lowering barriers to seasonal flu vaccines for their employees. The CDC is offering free seasonal influenza vaccines to farmworkers in high-risk states.

California has confirmed H5N1 avian influenza in additional dairy herds, bringing the total to 504 infected herds and approaching half of the state's dairy herds. See PHC alerts from 11/22, 11/21, and 11/15 for information about earlier totals. [Confidence: Very High]

Given California's proactive testing, the detection of an additional H5N1 case in a dairy worker is not unexpected. Businesses should follow the recommendations provided in the PHC analysis on October 22, including lowering barriers to seasonal flu vaccines for their employees. The CDC is offering free seasonal influenza vaccines to farmworkers in high-risk states.

California reported another case of H5N1 avian influenza in a dairy worker, totaling 31 dairy industry-related cases and 32 H5N1 cases in the state this year. No human-to-human spread of H5N1 has been detected. [Confidence: Very High]

PHC will monitor the event and provide updates as needed. No human-to-human spread of H5N1 has been detected. Businesses should follow the recommendations provided in the PHC analysis on October 22, including lowering barriers to seasonal flu vaccines for their employees.

H5N1 has been identified in a wastewater sample in Clark County, Nevada, the state's 1st H5N1 detection since a poultry outbreak in March 2023. An investigation is underway to determine the source. Nevada has not identified H5N1 in dairy cows or humans. [Confidence: Very High]

Given California's proactive testing, the detection of additional H5N1 cases in dairy workers is not unexpected. Businesses should follow the recommendations provided in the PHC analysis on October 22, including lowering barriers to seasonal flu vaccines for their employees. The CDC is offering free seasonal influenza vaccines to farmworkers in high-risk states.

California reported 2 new cases of H5N1 avian influenza in dairy workers, totaling 30 dairy industry-related cases and 31 H5N1 cases in the state this year. No human-to-human spread of H5N1 has been detected. [Confidence: Very High]

Businesses and individuals should dispose of any affected products. H5N1 avian flu and other pathogens have been found in raw milk. Pasteurization inactivates H5N1, making pasteurized milk and milk products safe to consume.

California issued an alert regarding a second recalled batch of cream top, whole raw milk from Raw Farm of Fresno County found to be contaminated with H5N1 avian flu. The affected milk is lot code 20241119 with a "best by" date of Dec 7. No illnesses have been identified tied to the contaminated product. [Confidence: Very High]

Businesses and individuals should dispose of any affected products. H5N1 avian flu and other pathogens have been found in raw milk. Pasteurization inactivates H5N1, making pasteurized milk and milk products safe to consume.

California issued an alert regarding one recalled batch of cream top, whole raw milk from Raw Farm of Fresno County found to be contaminated with H5N1 avian flu. The affected milk is lot code 20241109 with a "best by" date of Nov 27. No illnesses have been identified tied to the contaminated product. [Confidence: Very High]

For information only. Pennsylvania's decision to test milk for H5N1 is a proactive step in a state with no known cases. Businesses should follow the recommendations provided in the PHC analysis on October 22, including lowering barriers to seasonal flu vaccines for their employees.

Pennsylvania now requires bulk testing of milk for H5N1 from its farms. The decision is prompted by the steady increase of infected farms nationally; Pennsylvania has not found H5N1 in dairy herds. Farmers will not be responsible for the cost of testing, reducing a potential barrier to compliance. [Confidence: Very High]

California's proactive testing is expected to detect additional H5N1 cases in dairy herds. No human-to-human spread of H5N1 has been detected. Businesses should follow the recommendations provided in the PHC analysis on October 22, including lowering barriers to seasonal flu vaccines for their employees. The CDC is offering free seasonal influenza vaccines to farmworkers in high-risk states.

California has confirmed H5N1 avian influenza in 336 dairy herds in California since the start of the avian flu outbreak in cattle, up from 278 herds as of 11/15. The current count of known H5N1-infected herds represents ~30% of California's dairy herds. See PHC alerts from 11/15, 11/4, and 10/28 for information about earlier totals. [Confidence: Very High].

Given California's proactive testing, the detection of additional H5N1 cases in dairy workers is not unexpected. Businesses should follow the recommendations provided in the PHC analysis on October 22, including lowering barriers to seasonal flu vaccines for their employees. The CDC is offering free seasonal influenza vaccines to farmworkers in high-risk states.

Fresno County reported a case of H5N1 avian influenza in a Fresno County resident who had contact with infected cattle at a dairy farm in the Central Valley. This case is the 1st in Fresno County, and 24th in California. No human-to-human spread of H5N1 has been detected. [Confidence: Very High]

Ongoing testing in California and Utah is expected to detect additional H5N1 cases in dairy herds. No human-to-human spread of H5N1 has been detected. Businesses should follow the recommendations provided in the PHC analysis on October 22, including lowering barriers to seasonal flu vaccines for their employees. The CDC is offering free seasonal influenza vaccines to farmworkers in high-risk states.

California confirmed 45 new H5N1-infected dairy herds and Utah identified 4 new herds in the last week, totaling 278 in CA and 13 in UT. See PHC alerts from 10/28, 10/22, 10/10, 10/8, and 10/3 for information about earlier H5N1 detections in California herds. [Confidence: Very High]

Given California's proactive testing, the detection of additional H5N1 cases in dairy workers is not unexpected. No human-to-human spread of H5N1 has been detected. Businesses should follow the recommendations provided in the PHC analysis on October 22, including lowering barriers to seasonal flu vaccines for their employees. The CDC is offering free seasonal influenza vaccines to farmworkers in high-risk states.

Madera County, CA reported 2 human cases (1 confirmed and 1 presumptive) of H5N1 in workers with exposure to infected dairy cows. These are Madera County's 1st H5N1 human cases and CA's 22nd and 23rd. [Confidence: Very High]

California's proactive testing is expected to detect additional H5N1 cases in dairy herds. No human-to-human spread of H5N1 has been detected. Businesses should follow the recommendations provided in the PHC analysis on October 22, including lowering barriers to seasonal flu vaccines for their employees. The CDC is offering free seasonal influenza vaccines to farmworkers in high-risk states.

California has confirmed H5N1 avian influenza in 259 dairy herds in California since the start of the avian influenza outbreak in cattle, up from 233 herds as of 11/4. See PHC alerts from 11/4, 10/28, 10/22, 10/10, and 10/8 for information about earlier H5N1 detections in California herds. [Confidence: Very High]

For information only. The finding that 7% of tested dairy workers had evidence of past H5N1 infection is concerning and adds urgency to preventing coinfection of H5N1 and seasonal flu. Businesses should follow the recommendations provided in the PHC analysis from October 22. Businesses should lower barriers to seasonal flu vaccines for their employees.

In a study, CDC detected a 7% H5N1 infection rate in certain dairy workers. As seasonal flu season commences, this finding raises the probability of a farm worker being coinfected with H5N1 and seasonal flu, which increases the opportunities for H5N1 to gain the ability to transmit from person to person. Additionally, CDC recommended: (1) increased testing (2) wider Tamiflu use in those most likely to have simultaneous infection with H5N1 and seasonal flu (e.g., dairy and poultry workers), and (3) expanded PPE. [Confidence: Very High]

California's proactive testing is expected to detect additional human H5N1 cases. No human-to-human spread of H5N1 has been detected. Businesses should follow the recommendations provided in the PHC analysis on October 22, including lowering barriers to seasonal flu vaccines for their employees. The CDC is offering free seasonal influenza vaccines to farmworkers in high-risk states.

California reported its 21st human case of H5N1 avian influenza and another probable case in workers with exposure to cattle. The CDC confirmed 46 human H5N1 cases. As flu season begins, the potential for co-infection of H5N1 and a seasonal flu is concerning. [Confidence: Very High]

California's proactive testing is expected to detect additional human H5N1 cases. No human-to-human spread of H5N1 has been detected. Businesses should follow the recommendations provided in the PHC analysis on October 22, including lowering barriers to seasonal flu vaccines for their employees. The CDC is offering free seasonal influenza vaccines to farmworkers in high-risk states.

California reported the 17th, 18th, 19th human cases of H5N1 avian influenza on 11/1 and the 20th case on 11/4; all workers had exposure to cattle. There have been 44 total human cases of H5N1 avian influenza reported in the US. As flu season begins, the potential for co-infection of H5N1 and a seasonal flu is concerning. [Confidence: Very High]

California's proactive testing is expected to detect additional H5N1 cases in dairy herds. No human-to-human spread of H5N1 has been detected. Businesses should follow the recommendations provided in the PHC analysis on October 22, including lowering barriers to seasonal flu vaccines for their employees. The CDC is offering free seasonal influenza vaccines to farmworkers in high-risk states.

California has confirmed H5N1 avian influenza in 233 dairy herds in California since the start of the avian influenza outbreak in cattle. See PHC alerts from 10/28, 10/22, 10/10, 10/8, and 10/3 for information about earlier H5N1 detections in California herds. [Confidence: Very High]

It is unsurprising that mandatory surveillance detected H5N1 at multiple dairies in Cache County, Utah. Businesses should follow the recommendations provided in the PHC analysis on October 22, including lowering barriers to seasonal flu vaccines for their employees.

8 commercial dairies in Cache County, Utah have detected H5N1 avian influenza in cattle after the earlier detection of the dairy-related H5N1 strain in commercial poultry in the same county (PHC alert 10/15). Utah initiated mandatory surveillance for H5N1 in all Cache County dairies after the poultry outbreak (PHC alert 10/24). A quarantine has been instituted restricting movement of dairy cows at infected facilities with an exemption for slaughter. [Confidence: Very High]

Informational update only. Increased testing is likely to detect avian influenza in more dairy herds but aids in targeted use of biosecurity measures to limit further spread. Businesses should continue to follow the recommendations provided in the PHC analysis on Oct 22.

The USDA will begin a nationwide bulk milk testing program starting in early Nov. Bulk testing of milk for H5N1 has previously been conducted in CA and CO, and was used for brucellosis detection in the past. Bulk testing helps identify undetected virus circulation so that biosecurity measures can be implemented to limit spread. [Confidence: Very High]

For information only. Earlier PHC Alerts have covered the key points in the CDC's latest Bird Flu Response Update. Businesses should continue to follow the guidance in the 10/22 analysis. Businesses should lower barriers to seasonal flu vaccines for their employees.

The CDC has confirmed 36 total human H5 avian influenza cases: 20 related to dairy cattle, 15 related to poultry, and 1 without known animal exposure (CA: 16, WA: 6, CO: 10, MI: 2, MO: 1, TX: 1). 387 dairy herds have been found infected across 14 states, with most new infections being identified in California. All of CA’s 16 human cases were genotyped to the strain affecting cattle and had mild symptoms of eye redness/discharge and/or mild respiratory symptoms. [Confidence: Very High]

H5N1 infection in poultry workers culling birds is rare but not unexpected; the threat to business is unchanged. Businesses should lower barriers to seasonal flu vaccines for their employees. Businesses should follow the recommendations provided in the PHC analysis from October 22. PHC will continue to monitor and will communicate updated risk assessments as appropriate.

Washington state confirmed a 6th human case of H5N1. Two additional suspected cases have confirmatory tests pending. See PHC alerts from 10/28, 10/25, and 10/21 for more information on these cases in poultry workers. [Confidence: Very High]

Given California's proactive testing, the detection of additional H5N1 cases in dairy workers and herds is not unexpected. No human-to-human spread of H5N1 has been detected. Businesses should follow the recommendations provided in the PHC analysis on October 22, including lowering barriers to seasonal flu vaccines for their employees. The CDC is offering free seasonal influenza vaccines to farmworkers in high-risk states.

California has reported a new human H5N1 avian influenza case in an individual with animal exposure, the state's 16th reported case. Additionally, 178 dairies have been confirmed infected in Central California. [Confidence: Very High]

Informational update only. Multiple states have reported H5N1 avian flu outbreaks in dairy herds. Measures to reduce H5N1 in dairy herds (e.g., vaccines, biosecurity measures) can `protect against economic impacts and can reduce the risk of H5N1 gaining an ability to sustain transmission from person to person.

Two companies have been approved to conduct bovine H5N1 vaccine safety trials. One of the companies, Medgene, has already begun a field trial and expects the vaccine safety trial to be completed within 5 weeks. [Confidence: Very High]

H5N1 infection in poultry workers culling birds is rare but not unexpected; the threat to business is unchanged. Businesses should follow the recommendations provided in the PHC analysis on October 22. Businesses should lower barriers to seasonal flu vaccines for their employees. PHC will continue to monitor and will communicate updated risk assessments as appropriate.

Update on H5N1 avian influenza cases in Washington poultry workers (see PHC Alert 10/21): the CDC confirmed H5N1 in 2 of the 4 presumptively positive cases in Franklin County. Confirmatory testing of the other 2 cases is pending. The workers were likely exposed during culling of H5N1 infected poultry. There is no evidence of human-to-human transmission. [Confidence: Very High]

The detection of H5N1 in two humans without known animal exposure is concerning, but lack of evidence for human-to-human transmission is good news. Businesses should follow the recommendations provided in the PHC analysis on October 22, including lowering barriers to seasonal flu vaccines for their employees. PHC will continue to monitor and will communicate updated risk assessments as appropriate.

Update to the Missouri H5N1 avian flu (clade 2.3.4.4b) case (see PHC alert 9/6): a household contact's lab tests indicated previous infection, but all healthcare workers were negative. Because the case and the family member experienced flu-like symptoms at the same time, common exposure is more likely than person-to-person transmission. This H5N1 mostly impacts dairy cattle and poultry; all other human cases had known animal exposure. [Confidence: Very High]

Identification of the dairy-associated strain of H5N1 in poultry outbreaks can signal undetected H5N1-infected dairy herds in states that have not reported infected cattle. Businesses should follow the recommendations provided in the PHC analysis on October 22, including lowering barriers to seasonal flu vaccines for their employees.

On 10/15 USDA reported an avian influenza outbreak at a large commercial egg operation in Cache County. PHC warned that if genetic analysis identified the dairy-related version of H5N1, it could indicate Utah had undetected H5N1-infected dairy herds. The dairy strain was subsequently identified, and Utah initiated mandatory testing for avian influenza in all dairies in Cache County. [Confidence: Very High]

Given California's proactive testing, the detection of additional H5N1 cases in dairy workers is not unexpected. No human-to-human spread of H5N1 has been detected. Businesses should continue to follow the recommendations provided in the PHC analysis on Oct 22, including lowering barriers to seasonal flu vaccines for their employees. The CDC is offering free seasonal influenza vaccines to farmworkers in high-risk states.

California reported 1 new human H5N1 avian influenza case in a dairy worker, totaling 15 this year. Only animal-to-human transmission has been recorded in California, but additional human cases provide new opportunities for the virus to acquire genetic changes. As flu season begins, the potential for co-infection of H5N1 and a seasonal flu is concerning. See PHC alerts from 10/22, 10/18, 10/15, 10/11, and 10/9 for more details about earlier human H5N1 cases in dairy workers. [Confidence: Very High]

Businesses whose operations are sensitive to the price of milk should increase their uncertainty level around cost projections as the full impact of H5N1 infections on dairy herds develops.

Multiple media reports have cited Keith Poulsen, avian influenza researcher and Director of the Wisconsin Veterinary Diagnostic Laboratory, as asserting the mortality rate of California herds may be 15% - 20%, compared to the previously reported 2% in other states. The severe summer heat may be a factor. The reported 60-70% drop in milk production is also higher than previous estimates. Too little time has passed to know if infected cows will return to normal production for their next cycle. One source notes that younger cows are more impacted, which translates to the greatest financial impact since young cows have only just begun to produce milk. In combination, these factors could lead to significant losses to dairy farmers and volatility in milk and dairy product prices. [Confidence: Moderate]

Given California's proactive testing, the detection of additional H5N1 cases in dairy workers is not unexpected. No human-to-human spread of H5N1 has been detected. Businesses should follow the recommendations provided in the PHC analysis on October 22, including lowering barriers to seasonal flu vaccines for their employees. The CDC is offering free seasonal influenza vaccines to farmworkers in high-risk states.

Merced County Department of Public Health has reported the county's first human H5N1 case in a dairy worker at a farm with infected cattle. The worker's contacts have been notified and are being monitored for symptoms. This case is the 14th in California. See PHC alerts on 10/21 and 10/18 for information on other recent human H5N1 cases in the state. [Confidence: Very High]

Given California's proactive testing, the detection of additional H5N1 cases in dairy workers is not unexpected. No human-to-human spread of H5N1 has been detected. Businesses should continue to follow the recommendations provided in the PHC analysis on April 2, including lowering barriers to seasonal flu vaccines for their employees. The CDC is offering free seasonal influenza vaccines to farmworkers in high-risk states.

California has reported 2 new human H5N1 avian influenza cases in Central Valley dairy workers, totaling 13 this year. Only animal-to-human transmission has been recorded in California, but additional human cases provide new opportunities for the virus to acquire genetic changes. As flu season begins, the potential for co-infection of H5N1 and a seasonal flu is concerning. See PHC alerts from 10/18, 10/15, 10/11, and 10/9 for more details about earlier human H5N1 cases in dairy workers. [Confidence: Very High]

Detection of highly pathogenic avian influenza in more dairy herds is not unexpected. The continued spread of H5N1 throughout the US increases the risk of volatility in milk prices; businesses that purchase milk and dairy products should maintain low confidence in cost projections. Businesses should continue to follow the recommendations provided in the PHC analysis on April 26.

California has confirmed H5N1 avian influenza in 120 dairy herds in California since the start of the avian influenza outbreak in cattle while the US has confirmed H5N1 avian influenza in 320 herds. See PHC alerts from 10/10, 10/8, 10/3, 10/1, and 9/26 for information about earlier H5N1 detections in California herds. [Confidence: Very High]

Given California's proactive testing, the detection of additional H5N1 cases in dairy workers is not unexpected. No human-to-human spread of H5N1 has been detected, but additional human cases provide new opportunities for the virus to acquire genetic changes. As flu season begins, the potential for co-infection of H5N1 and a seasonal flu is concerning. Businesses should continue to follow the recommendations provided in the PHC analysis on April 2, including lowering barriers to seasonal flu vaccines for their employees. The CDC is offering free seasonal influenza vaccines to farmworkers in high-risk states.

California confirmed the 5 additional suspected human H5N1 avian influenza infections in dairy workers (PHC alert 10/15). The total case count is now 11. CA launched a new dashboard tracking confirmed and presumptive human H5N1 cases with information describing the symptoms in humans, poultry, and cattle. The new webpage also instructs individuals in high-risk jobs (farm workers, wildlife workers) on how to prevent H5N1 infections and spread. [Confidence: Very High]

For information only. Multiple states have reported highly pathogenic avian influenza (HPAI) outbreaks in dairy herds. Michigan's thorough surveillance for avian flu is likely to identify additional infected herds and farms.

Michigan has detected HPAI in a Clinton County dairy herd but no human cases have been detected associated with this infected herd. This is the 30th infected herd in Michigan. 305 HPAI-infected herds have been reported in the United States since the beginning of the outbreak. For more information on Michigan HPAI-infections see PHC alerts 9/23, 9/10, 8/27, 8/2, 7/11, 7/10, 5/30, 5/24, 5/22, 5/21, 5/17, 5/16, and 5/8. [Confidence: Very High]

Given California's proactive testing, the detection of additional H5N1 cases in dairy workers is not unexpected. No human-to-human spread of H5N1 has been detected, but additional human cases provide new opportunities for the virus to acquire genetic changes. As flu season begins, the potential for co-infection of H5N1 and a seasonal flu is concerning. Businesses should continue to follow the recommendations provided in the PHC analysis on April 2, including lowering barriers to seasonal flu vaccines for their employees.

California is proactively testing symptomatic individuals for bird flu, allowing for better surveillance and detection of human cases than in many other states. California has now identified 6 confirmed and 5 possible human cases. The cases had direct contact with infected dairy cattle at 9 different farms. [Confidence: Very High]

Businesses in Utah who purchase local eggs may see price fluctuations. The 1.8 million birds culled represent a significant portion of all the egg laying hens in the state (~6 million in 2022).

USDA reported the culling of 1.8 million chickens after avian influenza was identified in a "large commercial poultry flock” in northern Cache County. Nearby flocks have been quarantined. Detailed information about the flu type has not yet been released. Utah has not reported any H5N1 infected dairy herds; if the flock tests positive for the dairy strain of H5N1, it could indicate undetected dairy herd infections in the state. [Confidence: Very High]

Given the numerous dairy herd outbreaks in California, the detection of positive dairy workers is not unexpected. No human-to-human spread of H5N1 has been detected, but additional human cases provide new opportunities for the virus to acquire genetic changes. As flu season begins, the potential for co-infection of H5N1 and a seasonal flu is concerning. Businesses should continue to follow the recommendations provided in the PHC analysis on April 26.

Update to California's H5N1 cases among Central Valley dairy workers: one of the suspected new cases (see PHC alert 10/9) was confirmed to be positive. One other suspected case's confirmatory test is still pending. None of the human cases from California have had contact with one another and all cases are believed to be caused by contact with H5N1-infected dairy cows. [Confidence: Very High]

Detection of highly pathogenic avian influenza in more dairy herds is not unexpected. The continued spread of H5N1 throughout the US increases the risk of volatility in milk prices; businesses that purchase milk and dairy products should maintain low confidence in cost projections. Businesses should continue to follow the recommendations provided in the PHC analysis on April 26.

California reported 17 more H5N1-infected dairy herds, totaling 99 infected herds. Pasteurization inactivates the H5N1 virus, making pasteurized milk and milk products safe to consume. No sustained human-to-human spread of H5N1 has been detected. See PHC alerts from 10/8, 10/3, 10/1, and 9/24 for more information. [Confidence: Very High]

Given the numerous dairy herd outbreaks in California, the detection of positive dairy workers is not unexpected. No human-to-human spread of H5N1 has been detected, but additional human cases provide new opportunities for the virus to acquire genetic changes. As flu season begins, the potential for co-infection of H5N1 and a seasonal flu is concerning. Businesses should continue to follow the recommendations provided in the PHC analysis on April 26.

California has confirmed a 3rd human H5N1 avian influenza case in a Central Valley dairy worker (PHC alert 10/7). CA reported 2 more possible human cases located in the Central Valley. CDC is conducting confirmatory testing. None of the human cases from California have had contact with one another and all cases are believed to be derived from contact with H5N1-infected animals. [Confidence: Very High]

Detection of highly pathogenic avian influenza in more dairy herds is not unexpected. The continued spread of H5N1 throughout the US increases the risk of volatility in milk prices; businesses that purchase milk and dairy products should maintain low confidence in cost projections. Businesses should continue to follow the recommendations provided in the PHC analysis on April 26.

26 more H5N1-infected dairy herds were identified in California, bringing the total to 82 infected herds. Pasteurization inactivates the H5N1 virus, making pasteurized milk and milk products safe to consume. No sustained human-to-human spread of H5N1 has been detected. See PHC alerts from 10/3, 10/1, and 9/24 for more information. [Confidence: Very High]

Given the numerous dairy herd outbreaks in California, the detection of positive dairy workers is not unexpected. No human-to-human spread of H5N1 has been detected, but additional human cases provide new opportunities for the virus to acquire genetic changes. As flu season begins, the potential for co-infection of H5N1 and a seasonal flu is concerning. Businesses should continue to follow the recommendations provided in the PHC analysis on April 26.

California is investigating a 3rd possible case of H5N1 avian influenza case in a Central Valley dairy worker with no known connection to the prior 2 human cases in California (see PHC alert 10/3). Samples have been sent to CDC for confirmatory testing. [Confidence: Very High]

Given the numerous dairy herd outbreaks in California, the detection of two positive dairy workers is not unexpected. No human-to-human spread of H5N1 has been detected, but additional human cases provide the virus new opportunities to acquire genetic changes. As flu season begins, the potential for co-infection of H5N1 and a seasonal flu is concerning. Contacts of the cases are being monitored. Businesses should continue to follow the recommendations provided in the PHC analysis on April 26.

CDC tests have confirmed H5 avian influenza in 2 California dairy workers: a suspected case that the California Department of Public Health (CDPH) had previously announced (see earlier PHC alert 10/3) and a previously unreported individual. Both cases had mild symptoms, did not report respiratory symptoms, and were not hospitalized. [Confidence: Very High]

Evidence of previously undetected H5N1 infections among dairy workers means that other cases likely occurred/are occurring. No human-to-human spread of H5N1 has been detected. PHC will continue to monitor and will communicate updated risk assessments as appropriate. Businesses should continue to follow the recommendations provided in the PHC analysis on April 26.

California is investigating a possible case of H5N1 avian influenza case in a Central Valley dairy worker who handled H5N1-infected cattle. The preliminary test was positive for H5N1, and samples have been sent to CDC for confirmatory testing. The person's only symptom was conjunctivitis. 4 other US cases have been linked to the dairy industry since April (PHC alerts from 8/2, 7/5, and 5/30). [Confidence: Very High]

Hong Kong's import ban is a reminder that avian flu outbreaks can lead to economic losses. See PHC analysis on 4/26 for more information and guidance on the H5N1 dairy outbreaks.

Hong Kong's Centre for Food Safety implemented an import ban on all poultry and egg imports from Merced County, California, and Orange County, Florida due to H5N1 outbreaks in these areas. 40,950 tons of poultry meat and 13.86 million eggs were imported to Hong Kong from the US in the first six months of 2024. [Confidence: Very High]

Detection of highly pathogenic avian influenza in more dairy herds in multiple states is not unexpected. The continued spread of H5N1 throughout the US increases the risk of volatility in milk prices; businesses that purchase milk and dairy products should maintain low confidence in cost projections. Businesses should continue to follow the recommendations provided in the PHC analysis on April 26.

3 more H5N1-infected dairy herds were identified in California and 1 H5N1-infected dairy herd in Idaho, totaling 44 infected herds (CA) and 33 infected herds (ID) since the outbreak began. No human cases have been identified in these cattle outbreaks. Pasteurization inactivates the H5N1 virus, making pasteurized milk and milk products safe to consume. No sustained human-to-human spread of H5N1 has been detected. [Confidence: Very High]

Poultry exporters should be prepared for additional export bans if they operate in countries with ongoing avian influenza outbreaks. Cost of poultry products may increase in areas with bans on importation of poultry.

The Philippines banned the importation of live poultry, poultry products, and by-products from France after avian influenza started to spread within France in August (See PHC alert from 8/14). The Philippines regularly bans the import of birds and poultry products from countries with avian influenza outbreaks. [Confidence: Very High]

Symptomatic contacts of an H5N1 clade 2.3.4.4b avian flu case in an individual without known exposure to animals is a concerning new development. Follow up testing will help determine if human-to-human transmission may have occurred. Businesses do not currently need to change their posture regarding H5N1 influenza. PHC will continue to monitor and will communicate updated risk assessments as appropriate.

Update to the recent human H5N1 avian flu case in Missouri (see PHC alerts 9/23, 9/16, 9/13 and 9/6): respiratory symptoms have been reported in 4 additional health care workers who were exposed to the avian influenza H5N1 clade 2.3.4.4b case after respiratory droplet precautions were put into place. Of the 6 healthcare workers exposed, 1 tested negative for H5N1 through PCR while the others' antibody test results are pending. Missouri has reported no confirmed human-to-human transmission. See PHC Highly Pathogenic Avian Influenza (HPAI) H5N1 critical threat for more information. [Confidence: Very High]

Detection of highly pathogenic avian influenza in more dairy herds is not unexpected, though this is the largest number of infected herds in a state at one time. California produces about 20% of the US milk supply. The continued spread of H5N1 throughout the US increases the risk of volatility in milk prices; businesses that purchase milk and dairy products should maintain low confidence in cost projections. Businesses should continue to follow the recommendations provided in the PHC analysis on April 26.

6 more H5N1-infected dairy herds were identified in California, totaling 42 infected herds in Sept. No human cases have been identified in these cattle outbreaks. Pasteurization inactivates the H5N1 virus, making pasteurized milk and milk products safe to consume. No sustained human-to-human spread of H5N1 has been detected. [Confidence: Very High]

Colombia's import ban is a reminder that fear of avian flu outbreaks can lead to economic losses even when the disease is not identified in the affected product. See PHC analysis on 4/26 for more information and guidance on the H5N1 dairy outbreaks.

Colombia is once again allowing U.S. beef imports from all states, including those with H5N1 dairy herd outbreaks. In April, Colombia implemented import restrictions in response to H5N1 dairy herd outbreaks, the only country to do so. H5N1 has only been identified in dairy cows; some beef cows were tested, but found to be negative. [Confidence: Very High]

Detection of highly pathogenic avian influenza in more dairy herds is not unexpected, though this is the largest number of infected herds in a state at one time. California produces about 20% of the US milk supply. The continued spread of H5N1 throughout the US increases the risk of volatility in milk prices; businesses that purchase milk and dairy products should maintain low confidence in cost projections. Businesses should continue to follow the recommendations provided in the PHC analysis on April 26.

18 more H5N1-infected dairy herds were identified in California, totaling 31 infected herds in Sept. No human cases have been identified in these cattle outbreaks. Pasteurization inactivates the H5N1 virus, making pasteurized milk and milk products safe to consume. No sustained human-to-human spread of H5N1 has been detected. [Confidence: Very High]

Evidence of longer term economic impacts on dairy farms from H5N1 outbreaks increases the potential for supply chain challenges and product cost fluctuations. No sustained human-to-human spread of H5N1 has been detected. Businesses should continue to follow the recommendations provided in the PHC analysis on April 26.

Michigan dairy farms have reported aborted calves, milk production losses, and livestock death from the highly pathogenic avian influenza (HPAI) H5N1 outbreak among dairy cattle. 29 dairy herds have been infected in Michigan, totaling 232 livestock herds across the US. On one farm in Michigan, milk production decreased by 25%, and 5% of the herd had to be culled resulting in $100K losses. [Confidence: Very High]

Symptomatic close contacts of an H5N1 clade 2.3.4.4b avian flu case in an individual without known exposure to animals is a concerning new development. Follow up testing could help determine if human-to-human transmission may have occurred. Businesses do not currently need to change their posture regarding H5N1 influenza. PHC will continue to monitor and will communicate updated risk assessments as appropriate.

Update to the recent human H5N1 avian flu case in Missouri (see PHC alerts 9/16, 9/13 and 9/6): a second close contact was identified, consisting of a healthcare worker who developed symptoms, but was never tested. Health officials are considering conducting follow up testing to determine if the close contacts may have evidence of previous H5N1 infection. CDC can only assist with an invitation from the state. [Confidence: Very High]

The detection of highly pathogenic avian influenza in more dairy herds is not unexpected. California produces about 20% of the US milk supply. The continued spread of H5N1 throughout the US increases the risk of volatility in milk prices; businesses that purchase milk and dairy products should maintain low confidence in cost projections. Pasteurization inactivates the H5N1 virus, making pasteurized milk and milk products safe to consume. No sustained human-to-human spread of H5N1 has been detected. Businesses should continue to follow the recommendations provided in the PHC analysis on April 26.

Six dairy herds in California tested positive for highly pathogenic avian influenza (HPAI) H5N1, totaling 17 dairy herd outbreaks in the state. No human cases have been identified in this current outbreak. [Confidence: Very High]

Informational update only.

Massachusetts tested its 95 licensed dairy herds for H5N1 and tests confirmed all were negative. MA is the 1st state to proactively test all herds for H5N1. [Confidence: Very High]

Informational update only. Multiple states have reported H5N1 avian flu outbreaks in dairy herds. Increased surveillance for avian flu is likely to identify additional infected herds and farms.

Two dairy herds in Texas tested positive for highly pathogenic avian influenza (HPAI) H5N1, totaling 26 dairy herd outbreaks in the state. TX's last infected dairy herd was in Aug. No human cases have been identified in this current outbreak. [Confidence: Very High]

For informational purposes only. Canada's recommendation that farmers not bring cattle to major livestock events illustrates the ripple effects of outbreaks to business. PHC will continue to monitor the avian influenza H5N1 outbreak in cattle.

Due to the highly pathogenic avian influenza (HPAI) H5N1 outbreak currently spreading across the USA, Canada has advised farmers to not move cattle across international boundaries for USA agricultural exhibitions. [Confidence: Very High]

Informational update only. Multiple states have reported H5N1 avian flu outbreaks in dairy herds. Increased surveillance for avian flu is likely to identify additional infected herds and farms.

A dairy herd in Idaho tested positive for highly pathogenic avian influenza (HPAI) H5N1, the state's 34th dairy herd outbreak. ID's last infected dairy herd was in Aug. No human cases have been identified in this current outbreak. [Confidence: Very High]

The detection of an H5N1 clade 2.3.4.4b avian flu case in an individual without known exposure to animals is a concerning new development. Businesses do not currently need to change their posture regarding H5N1 influenza. PHC will continue to monitor and will communicate updated risk assessments as appropriate.

CDC reported that the recent human avian flu case in Missouri (see PHC alerts 9/13 and 9/6) was confirmed to be H5N1 clade 2.3.4.4b, closely related to the strain that has been infecting dairy cows. The case had a household contact who became symptomatic on the same day as the case but was never tested. [Confidence: Very High]

Informational update. The detection of high levels of H5N1 in wastewater is concerning but not surprising; it does not require an immediate business response. The wastewater samples indicate the strain is persisting and that interventions like limiting livestock movement will not eradicate the strain as USDA hoped. Ongoing H5N1 infections offer the virus more opportunities to adapt to humans. PHC will continue to monitor H5N1 and update businesses as necessary.

Researchers reported H5N1 avian influenza in wastewater samples in 10 Texan cities and at 22/23 wastewater sampling sites. Their analysis suggests multiple animal sources contributed to the detection. H5N1 had already been discovered in Texas wastewater in spring 2024. See PHC Highly Pathogenic Avian Influenza (HPAI) H5N1 critical threat for more information. [Confidence: Very High]

Informational update only. Australia has reported periodic avian flu outbreaks at poultry farms.

Victoria, Australia loosened some poultry industry restrictions following 2 months with no new avian flu cases. The last avian flu outbreak in Victoria was June 24. Former restricted areas have been reduced to control areas, which allows for animal movement and poultry no longer confined inside. [Confidence: Very High]

The detection of an H5 avian influenza case in a patient without known exposure to animals is a concerning new development. Businesses do not currently need to change their posture regarding H5N1 influenza. PHC will continue to monitor and will communicate updated risk assessments as appropriate.

CDC reported that the recent H5 human case in Missouri (see PHC alert 9/6) had no clear exposure source. The case was deemed a "one off" with no increased risk of other human cases tied to this situation. [Confidence: Very High]

The detection of highly pathogenic avian influenza in another dairy herd is not unexpected. The continued spread of H5N1 throughout the US increases the risk of volatility in milk prices; businesses that purchase milk and dairy products should maintain low confidence in cost projections. Businesses should continue to follow the recommendations provided in the PHC analysis on April 26.

California identified H5N1 avian flu in 2 more dairy herds, totaling 5 infected herds this week and 8 in CA this year. No human cases have been detected associated with the California outbreak and no human-to-human spread of H5N1 has been detected. California produces about 20% of the US milk supply. Pasteurization inactivates the H5N1 virus, making pasteurized milk and milk products safe to consume. [Confidence: Very High]

The detection of highly pathogenic avian influenza in another dairy herd is not unexpected. California produces about 20% of the US milk supply. The continued spread of H5N1 throughout the US increases the risk of volatility in milk prices; businesses that purchase milk and dairy products should maintain low confidence in cost projections. Pasteurization inactivates the H5N1 virus, making pasteurized milk and milk products safe to consume. No human-to-human spread of H5N1 has been detected. Businesses should continue to follow the recommendations provided in the PHC analysis on April 26.

California identified H5N1 avian flu in 3 dairy herds in Central Valley, totaling 6 infected dairy herds in the state this year. No human cases have been detected associated with this outbreak. [Confidence: Very High]

Multiple states have reported H5N1 avian flu outbreaks in dairy herds. Increased surveillance for avian flu is likely to identify additional infected herds and farms.

A dairy herd in Shiawassee County, Michigan has tested positive for highly pathogenic avian influenza (HPAI) H5N1. This is the 29th dairy herd to test positive for HPAI in the state. No human cases have been identified in this current outbreak. [Confidence: Very High]

The detection of an H5 avian influenza case in a patient without known exposure to animals is a concerning new development. Businesses do not currently need to change their posture regarding H5N1 influenza. PHC will continue to monitor and will communicate updated risk assessments as appropriate.

Missouri reported its 1st human case of avian influenza A (H5). This case was discovered through routine influenza surveillance system as opposed to surveillance triggered by recent cattle outbreaks. As flu surveillance activity accelerates with the start of flu season, PHC will monitor closely for evidence of H5 becoming more common in people. See PHC Highly Pathogenic Avian Influenza (HPAI) H5N1 critical threat for more information. [Confidence: Very High]

The detection of highly pathogenic avian influenza in another dairy herd is not unexpected. No human-to-human spread of H5N1 has been detected. Businesses should continue to follow the recommendations provided in the PHC analysis on April 26.

Curry County, New Mexico reported a dairy herd infected with H5N1 avian flu, the state's 9th dairy herd outbreak. This is NM's 1st dairy herd outbreak since April. No human cases have been detected associated with this outbreak. [Confidence: Very High]

The detection of highly pathogenic avian influenza in another dairy herd is not unexpected. California produces about 20% of the US milk supply and the affected herds are in counties that produce over half of CA's milk output. The continued spread of H5N1 throughout the US increases the risk of volatility in milk prices; businesses that purchase milk and dairy products should maintain low confidence in cost projections. Pasteurization inactivates the H5N1 virus, making pasteurized milk and milk products safe to consume. No human-to-human spread of H5N1 has been detected. Businesses should continue to follow the recommendations provided in the PHC analysis on April 26.

California confirmed that 3 dairy herds tested for positive for H5N1 avian flu (see PHC alert 8/30), the state's 1st H5N1 detection in dairy cows. CA is the 13th state to identify H5N1 among dairy herds. The affected herds are in Tulare, Merced, and Stanislaus counties. No human cases have been detected associated with this outbreak. [Confidence: Very High]

Businesses with interests in dairy may want to discuss milk testing programs and biosecurity measures such as worker PPE. No federally mandated bulk milk testing program has been implemented. The USDA has created a voluntary pilot weekly bulk milk testing program, which will reimburse farmers for lost milk production. Currently, only 33 dairy herds are being monitored nationally (1 in California).

California reported investigating 3 dairy herds for H5N1 avian influenza. So far, 13 states have had dairy cattle test positive for H5N1. H5N1 can spread between wild birds, cattle, poultry, and between farms by farmworkers. [Confidence: Very High]

Informational update only. Multiple states have reported H5N1 avian flu outbreaks in dairy herds. An H5N1 vaccine, used in conjunction with current biosecurity measures, could help minimize or control dairy herd outbreaks.

The USDA announced that field trials will be conducted with a new H5N1 vaccine for use in dairy cows. The trial will assess vaccine safety, the first step towards widespread use of a vaccine. If the vaccine is found to be safe, effectiveness would be assessed next. [Confidence: Very High]

Multiple states have reported H5N1 avian flu outbreaks in dairy herds. Increased surveillance for avian flu is likely to identify additional infected herds and farms.

Van Buren County, Michigan reported an H5N1 outbreak in a dairy herd, the state's 28th avian flu outbreak in a dairy herd this year. Michigan last reported a dairy herd H5N1 outbreak in late July. No human cases have been identified with this current outbreak. [Confidence: Very High]

Informational update only. See PHC analysis on 4/26 for more information and guidance on the H5N1 avian flu outbreak.

The second round of testing for live H5N1 virus in commercial dairy products were all found to be negative for live virus. 167 samples were tested from retail products, including aged raw milk cheese, pasteurized milk, and products made from pasteurized milk, such as pasteurized cheeses, cream cheese, butter, and ice cream. See PHC alerts 7/5 and 7/1 about earlier testing studies with commercial dairy products for H5N1. [Confidence: Very High]

Multiple states have reported H5N1 avian flu outbreaks in dairy herds. Increased surveillance for avian flu is likely to identify additional infected herds and farms.

USDA announced that they will add H5N1 avian flu to routine testing of culled dairy cows as part of their surveillance program, the National Residue Program (NRP). H5N1 testing will begin Sept 16. [Confidence: Very High]

Informational update only. Increased surveillance for avian flu is likely to identify additional infected herds and farms.

Colorado reported another H5N1 outbreak in a dairy herd. This outbreak is occurring in a herd that had previously been infected in the spring. This is Colorado's 63rd dairy herd outbreak since April. [Confidence: Very High]

Informational purposes only. Testing lactating cows participating in the State Fair reflects the ongoing concern about avian flu transmission between cows and humans.

The Nebraska State Fair is requiring H5N1 testing of all participating lactating dairy cows amid avian flu concerns. Nebraska has not identified any H5N1-infected dairy herds, but bordering states Colorado, Kansas and Iowa have all had dairy outbreaks. [Confidence: Very High]

Informational update only. Increased surveillance for avian flu is likely to identify additional infected herds and farms.

Colorado reported 9 more H5N1 outbreaks among dairy herds, all detected via their required bulk-tank milk testing. Colorado has identified 63 H5N1-infected dairy herds since April. [Confidence: Very High]

Colorado, South Dakota, and Texas have reported new avian flu outbreaks in dairy herds. Increased surveillance for avian flu is likely to identify additional infected herds and farms.

H5N1 avian flu was detected in 3 more dairy herds in the last week, totaling 181 dairy herd outbreaks from 13 states during 2024. The newest dairy herd outbreaks were identified in Colorado, South Dakota, and Texas. [Confidence: Very High]

Informational update only. Enterprise businesses are not directly affected, but detection of H5N1 in new mammal species illustrates that the disease continues to spread to new animal groups. See PHC analysis on 4/26 for more information and guidance on this outbreak.

Weld County, Colorado reported detection of highly pathogenic avian influenza H5N1 in 3 new mammal species: deer mouse, prairie vole, and desert cottontail rabbit. [Confidence: Very High]

Evidence of previously undetected H5N1 infections among dairy workers means that other cases likely occurred/are occurring. No human-to-human spread of H5N1 has been detected. Businesses should continue to follow the recommendations provided in the PHC analysis on April 26.

Researchers reported that 2 Texas farmworkers had H5N1 antibodies, indicating that they had previously been infected with H5N1. Testing was done as part of a surveillance project on 2 Texas farms that had previously responded to an H5N1 outbreak among their cattle herds. [Confidence: Very High]

Michigan has reported avian flu outbreaks among dairy herds and poultry farms. Increased surveillance for avian flu is likely to identify additional infected herds and farms.

Michigan reported that H5N1 has been detected in another of their dairy herds, this one in a farm in Van Buren County. This is the 27th H5N1-infected herd in Michigan. [Confidence: Very High]

Informational update only.

CDC announced it will offer free seasonal flu vaccine to farm workers this fall. Dairy and poultry workers are at increased risk for H5N1 avian flu infection. Seasonal flu vaccine helps prevent seasonal flu infection but does not protect against H5N1 infection. Co-infection increases the risk of H5N1 mutating and becoming more transmissible to humans. [Confidence: Very High]

Informational update only.

WHO announced initiation of a program for pre-clinical H5N1 mRNA vaccine development. WHO will partner with Argentinian vaccine manufacturer Sinergium Biotech through the Technology Transfer Programme which aims to strengthen mRNA vaccine manufacturing capability in low- and middle-income countries. Findings will be shared with other manufacturing partners after pre-clinical development is complete. [Confidence: Very High]

Informational purposes only. Banning lactating cows from the State Fair reflects the ongoing concern about avian flu transmission between cows and humans.

Minnesota reported banning birthing cows and newborn calves from the 2024 Minnesota State Fair due to concerns about avian flu spreading. Dairy cow-calf pairs can participate as long as the mother is not lactating. [Confidence: Very High]

Human cases of highly pathogenic avian influenza in poultry farm workers exposed to infected birds are not unexpected. No human-to-human spread of H5N1 has been detected. Businesses should continue to follow the recommendations provided in the PHC analysis on April 26.

Colorado reported 3 new human cases of H5N1 in poultry farm workers, totaling 10 human cases of H5N1 in Colorado this year. All 3 new cases had mild disease and worked at the same poultry farm in Weld County. This is the 2nd poultry farm in Weld County that has identified human cases of H5N1 (see PHC alerts 7/15 and 7/22 for info on previous cases). [Confidence: Very High]

Colorado has reported avian flu outbreaks among dairy herds, poultry farms, and human cases who work with infected animals. Increased surveillance for avian flu is likely to identify additional infected herds and farms.

The Colorado Department of Agriculture is mandating highly pathogenic avian flu (HPAI) testing of all commercial dairy cow bulk-tanks. Colorado has reported 2 spillover events in July involving an HPAI strain in dairy cows being detected in commercial poultry farms. [Confidence: Very High]

Human cases of highly pathogenic avian influenza in poultry farm workers exposed to infected birds is not unexpected. No human-to-human spread of H5N1 has been detected. Businesses should continue to follow the recommendations provided in the PHC analysis on April 26.

Colorado reported a new human case of H5N1 in a poultry farm worker and confirmed a previously suspected case (see PHC alert 7/15 for info). So far, 10 human cases of H5 avian flu have been identified in the US, 4 exposed to sick cows and 6 to sick poultry. [Confidence: Very High]

Colorado has had H5N1 outbreaks in both dairy herds and poultry farms. Businesses should continue to follow the recommendations provided in the PHC analysis on April 26.

Colorado officials reported 5 more dairy herds infected with H5N1, totaling 116 infected herds across 13 states so far. No new human cases have been identified. [Confidence: Very High]

April milk samples from a farm in Oklahoma were recently submitted for testing when the business sought reimbursement for lost milk production. These cows are the first known H5N1 cases in Oklahoma. Businesses should continue to follow the recommendations provided in the PHC analysis on 4/26.

Oklahoma reported detection of H5N1 in a dairy herd, making it the 13th state to have H5N1-infected dairy cows. The samples were collected in April 2024, but not sent for testing until July. The delay underscores the significant gaps in H5N1 surveillance. Oklahoma has not reported any H5N1-infected birds in the state in 2024. No human cases have been identified with this new outbreak. [Confidence: Very High]

Michigan and Minnesota have had H5N1 outbreaks in dairy herds and birds, so infected domestic cats in the affected areas are not unexpected. Businesses should continue to follow the recommendations provided in the PHC analysis from April 26.

3 cats tested positive for H5N1 avian influenza, 2 from Minnesota and 1 from Michigan. The 2 infected cats from Minnesota live on a dairy farm that has reported H5N1 in their herd. The cat from Michigan lives in the same county that has reported H5N1 in dairy herds. [Confidence: Very High]

Benton County, Minnesota has had H5N1 outbreaks in dairy herds and birds, so this newest dairy herd outbreak is not unexpected. Businesses should continue to follow the recommendations provided in the PHC analysis from April 26.

Benton County, Minnesota reported a dairy herd infected with H5N1 avian flu, totaling 9 infected herds in the state this year. This is the 4th infected herd in Benton County. [Confidence: Very High]

Gratiot County has had H5N1 outbreaks in both dairy herds and poultry farms, so this newest dairy herd outbreak is not unexpected. Businesses should continue to follow the recommendations provided in the PHC analysis on April 26.

Gratiot County, Michigan reported a new H5N1 avian influenza outbreak in a dairy herd, the first dairy herd outbreak in the state since June 7 and the 26th Michigan herd affected. No human cases have been identified with this new outbreak. [Confidence: Very High]

Businesses with eggs sourced from Colorado should assess their supply chains. H5N1 in poultry presents low risk to humans.

Colorado declared a state emergency after identifying an H5N1 avian influenza outbreak in a large commercial poultry farm in Weld County. About 1.8 million chickens will be culled, the 2nd largest in the state's history. Poultry quarantine and movement ban have been implemented. [Confidence: Very High]

This newest study provides further evidence that drinking raw milk may pose an infection risk. Pasteurization inactivates the H5N1 virus, making pasteurized milk and milk products safe to consume.

The FDA reported results from a study indicating that 14% of raw milk samples tested were found to contain infectious H5N1 avian flu. The study involved testing raw milk from 4 states with dairy herds infected with H5N1 avian flu. This is the same study described in PHC alert on 7/1. [Confidence: Very High]

Another human case of highly pathogenic avian influenza in a dairy worker exposed to infected cows is not unexpected. No human-to-human spread of H5N1 has been detected. Businesses should continue to follow the recommendations provided in the PHC analysis on April 26.

A 4th human case of avian flu tied to the US dairy industry has been identified, the first case in Colorado. The case works at a dairy farm with cows who have tested positive for H5N1. Preliminary testing indicates the case's strain is H5 and is likely to be H5N1 given exposure to infected cows, but full genetic testing is pending. The case only has eye symptoms. [Confidence: Very High]

This newest study provides further evidence that pasteurization inactivates the H5N1 virus, making pasteurized milk and milk products safe to consume.

The FDA reported results from a study confirming that pasteurization kills H5N1 avian flu in milk and milk products. The study involved inoculating homogenized raw milk with higher levels of H5N1 virus than those found in samples of contaminated raw milk, pasteurizing it using typical pasteurization time and temperature requirements, and then checking for live virus. Results indicate that pasteurization inactivated the virus. [Confidence: Very High]

Businesses should expect the detection of avian influenza to continue. At this point, widespread disruption to the milk supply is not anticipated.

An eleventh dairy herd in Iowa has reported positive HPAI detection. Iowa is considering adopting testing requirements similar to those implemented in Wisconsin for animals brought to agricultural fairs to reduce the risk of cow-to-human transmission. See PHC Alert from 6/17 for related information. [Confidence: Very High]

Businesses should expect the detection of avian influenza to continue. At this point, widespread disruption to the milk supply is not anticipated.

A fourth dairy herd in Sioux County, Iowa tested positive for avian influenza, bringing the total number of herds in Iowa impacted to six. Iowa is considering adopting testing requirements similar to those implemented in Wisconsin for animals brought to agricultural fairs to reduce the risk of cow-to-human transmission. [Confidence: Very High]

Informational update only.

USDA APHIS reported that 36 more house mice in Roosevelt County, New Mexico have tested positive for H5N1 avian influenza, totaling 47 so far. The mice were found at a poultry farm in New Mexico that also had a red fox that tested positive for H5N1. See PHC alert 6/5 for more info. [Confidence: Very High]

Informational update. Dairy cattle in the state have tested positive for the disease, and infected cattle or birds are the most likely source of the wastewater detection. Despite the flurry of recent media reports, there is no evidence that these outbreaks pose a substantial threat to humans.

Harris County, Texas reported detection of H5N1 avian influenza in wastewater samples. H5N1 was detected in 3 Texas dairy herds earlier this month. No human cases have been reported in the greater Houston area. [Confidence: Very High]

Informational update only. This story highlights the flexibility of avian influenza in expanding its host range among mammals, and the ongoing risk this disease poses to human populations. Businesses should continue to follow the recommendations provided in the PHC analysis on April 26.

The H5N1 avian influenza strain involved in the human case in Texas was found to cause severe disease in ferrets. Ferrets are often used as a surrogate for human disease. Unlike seasonal flu, H5N1 was transmitted between ferrets via direct contact but not through respiratory droplets. [Confidence: Very High]

The detection of highly pathogenic avian influenza in another dairy herd is not unexpected. No human-to-human spread of H5N1 has been detected. Businesses should continue to follow the recommendations provided in the PHC analysis on April 26.

Highly pathogenic avian influenza has been confirmed in a Wyoming dairy herd, Wyoming's first detection. It is the 12th state to detect H5N1 in dairy cattle. The exact location of the affected herd has not been released. [Confidence: Very High]

Informational update. Dairy cattle in the state have tested positive for the disease, and infected cattle or birds are the most likely source of the wastewater detection. Despite the flurry of recent media reports, there is no evidence that these outbreaks pose a substantial threat to humans.

Austin-Travis County, Texas reported detection of traces of H5N1 in wastewater samples. H5N1 was detected in 3 Texas dairy herds earlier this month. No human cases have been reported in Austin. [Confidence: Very High]

The detection of highly pathogenic avian influenza in another dairy herd is not unexpected. No human-to-human spread of H5N1 has been detected. Businesses should continue to follow the recommendations provided in the PHC analysis on April 26.

H5N1 has been confirmed in a Benton County dairy herd, Minnesota's first detection. It is the 11th state to detect H5N1 in dairy cattle. Stearns County reported H5N1 outbreaks in turkeys earlier this week.

The detection of highly pathogenic avian influenza in another dairy herd is not unexpected, especially given the recent H5N1 outbreak in a poultry farm in a neighboring county. No human-to-human spread of H5N1 has been detected. Businesses should continue to follow the recommendations provided in the PHC analysis on April 26.

Highly pathogenic avian influenza was identified in a new dairy herd in O'Brien County, Iowa, making Iowa the 10th state to reported infected livestock. Iowa is the 10th-leading milk-producing state. Neighboring Sioux County, IA recently reported an H5N1 outbreak among poultry. No new US human H5N1 cases have been identified since the last case on May 30. See PHC alerts 4/1, 5/22, and 5/30 for more info. [Confidence: Very High]

USDA APHIS added house mice to the list of mammals infected with H5N1. Media reports indicate the mice were at a dairy farm that has had infected cattle.

USDA APHIS reported that 11 wild house mice in Roosevelt County, New Mexico have tested positive for H5N1 avian influenza. The mice may have become infected after drinking raw milk from infected dairy cattle. [Confidence: Very High]

Informational update only.

The USDA has begun enrolling farms in its Voluntary H5N1 Dairy Herd Status Pilot Program, which aims to increase testing options and improve H5N1 surveillance. Farms participating in the program can test milk pooled from multiple animals instead of testing animals individually. Further, farms can be declared disease-free and allowed to resume animal transport if they test negative for three consecutive weeks. This program aims to ease the testing burden placed on farms by the April 24, 2024 federal testing order while still maintaining a high level of surveillance. [Confidence: Very High]

Informational update. Other dairy cattle in the state have tested positive for the disease and infected cattle remain the most likely source of these wastewater detections. Despite the flurry of recent media reports, there is no evidence that these outbreaks pose a substantial threat to human or cattle populations.

Wastewater surveillance has identified H5N1 in North Carolina area where no previous outbreak had been detected. [Confidence: Very High]

Informational update. Articles in previous weeks had presented the question of whether spikes in influenza A activity in San Francisco wastewater may result from undetected avian influenza spread. This most recent announcement confirms that the disease is present in the state but further confirms that it constitutes a small portion of the influenza A genetic material in local wastewater samples and is absent in the most recent testing.

The San Francisco Department of Health has announced that two chickens at a wild bird market sampled at least 10 days ago have tested positive for H5N1. Testing of San Francisco wastewater at around the same time showed traces of H5N1, though follow-up testing failed to confirm the presence of the virus. The infected birds were asymptomatic and no additional cases of H5N1 in birds or humans have been reported. [Confidence: Very High]

Informational update. These data reinforce that avian influenza genetic material is detectable within wastewater systems, though most detections are in areas of known activity. Despite the flurry of recent media reports, there is no evidence that these outbreaks pose a substantial threat to human or cattle populations.

WastewaterScan, a wastewater monitoring partnership between Stanford and Emory Universities, has launched its H5 avian influenza monitoring system. Over the month of May, several wastewater samples from Michigan, Texas, Minnesota, Iowa, and Idaho tested positive for H5 influenza. Since the peak of detections in mid-May, the level of activity has steadily declined. [Confidence: Very High]

The detection of a third positive farm worker is not unexpected, but the presence of respiratory symptoms in this person combined with the mutation noted in last week's case in Michigan changes the overall picture. No human-to-human spread of H5N1 has been detected with this outbreak, but these developments reflect some of the necessary changes for the virus to acquire this ability. Contacts of the cases are being monitored. Businesses should continue to follow the recommendations provided in the PHC analysis on April 26.

A 3rd human case of avian influenza H5N1 tied to the US dairy industry has been identified, the first person in this outbreak to have respiratory symptoms. The new case is a dairy farm worker in Michigan with no ties to the previous 2 cases. See PHC alerts 4/1 and 5/22 for more info. [Confidence: Very High]

Businesses with eggs sourced from Iowa should assess their supply chains and expect price fluctuations in response to production shortfall.

Highly pathogenic avian influenza (HPAI) was detected in a commercial poultry flock in Sioux County, Iowa, the first in Iowa in 2024. HPAI was last detected in Iowa in fall 2023. Over 4 million chickens in the affected flock will be culled. [Confidence: Very High]

Enterprise businesses are not directly affected, but detection of H5N1 in alpacas illustrates that the disease is spreading to new animal groups and to more areas. Businesses should continue to follow the recommendations provided in the PHC analysis on April 26.

Alpaca have not previously tested positive for H5N1, but given the many other mammals that have been infected, this finding is not completely unexpected. The strain in the alpaca was the same as in poultry that had been culled on the premises; it is also the same as the strain found in US dairy cattle. [Confidence: Very High]

Prior studies have found H5N1 is inactivated when proper food safety cooking recommendations are followed. Businesses should continue to follow food safety protocols when handling and cooking beef. See PHC analysis on 4/26 for more information and guidance on this outbreak.

Diverted cows are not allowed to enter the food chain. To date, one cow of the 96 cows tested has been positive for H5N1. No meat from these dairy cattle entered the food supply. [Confidence: Very High]

Businesses should not stock raw milk to avoid liability due to numerous diseases that can be transmitted in unpasteurized milk.

A laboratory study found mice that consumed raw milk positive for H5N1 contained high virus titers, indicating infection. Prior studies have confirmed that pasteurization inactivates the H5N1 virus, making it safe to drink. [Confidence: Very High]

The detection of H5N1 in additional dairy herds is not unexpected and does not indicate an immediate change in overall risk. Businesses should continue to follow the recommendations provided in the PHC analysis on April 26.

H5N1 was detected in 7 new US dairy herds this week in Michigan (4 herds), Idaho (1), and Texas (1). See PHC alerts 4/1, 4/29, and 5/21 for more info. [Confidence: Very High]

The detection of a second positive farm worker is not unexpected and does not indicate an immediate change in overall risk. Businesses should continue to follow the recommendations provided in the PHC analysis on April 26.

Michigan reported its first human case of H5N1 avian influenza in a farmworker who worked with livestock infected with H5N1. This is the first human case of H5N1 since March 29. See PHC alerts 4/1 and 4/29 for more info. [Confidence: Very High]

Human cases of H5N1 are rare; the risk of an outbreak is extremely low. Employees in or traveling to countries where human H5N1 cases have been identified, such as Vietnam or India, should avoid live-animal markets and not have contact with or consume diseased poultry.

Australia reported a human case of H5N1, the first time H5N1 has been identified in a person or animal in Australia. The case is a child with a history of travel to India. Close contacts were monitored, but have not tested positive. [Confidence: Very High]

Informational update only.

Michigan reported that 3 more dairy herds have tested positive for H5N1, affected counties include Clinton, Gratiot, and Ionia. 18 dairy herds in MI have now had positive tests among their cows. [Confidence: Very High]

H5N1 in eggs and poultry is killed by cooking; a new study results find the same for cooked beef. USDA recommends cooking beef to 160 degrees (well done). See PHC analysis on 4/26 for more information and guidance on this outbreak.

A USDA study found that fully cooking beef inactivates the H5N1 virus, making it safe to eat. The study involved inoculating beef patties with an H5N1 virus surrogate, cooking it to different temperatures, and then checking for live virus. Results indicate that cooking the beef to medium or well done fully inactivated the virus. The study was conducted after H5N1 was found to infect dairy cows; there were concerns about beef cows becoming infected or posing a risk to the commercial beef supply. [Confidence: Very High]

Businesses with eggs sourced from Michigan should assess their supply chains and expect price fluctuations in response to production shortfall.

Herbruck’s Poultry Ranch, Michigan's largest commercial egg producer, reported laying off 400 workers across 5 facilities. Due to H5N1, many commercial bird flocks are being culled--reducing the need for labor--and facilities decontaminated to prevent the spreading of H5N1, the first time this has been done in MI. Avian flu has affected the poultry industry since 2022, but this is the first time the commercial egg industry has been affected. Herbruck’s reported that they intend for the layoffs to be temporary. [Confidence: Very High]

Informational update only.

The USDA reported that H5N1 has been detected in 3 new dairy herds, 2 in Michigan and 1 in Idaho. 9 states have detected H5N1 in dairy herds, with Michigan having the most outbreaks (14). [Confidence: Very High]

Detecting H5N1 in urban wild birds in NYC is not surprising since migratory birds interact with urban bird populations, but this has not been well documented. The current risk of human disease is low, but individuals should not interact with wild birds.

Researchers reported that 6 of 1,792 samples collected from wild birds in New York City tested positive for H5N1. The positive samples were found in a red tail hawk, Canadian geese, a Peregrine falcon, and a chicken. The H5N1 strains were a mix of Eurasian and North American avian flu viruses. [Confidence: Very High]

Informational update only.

19 of 23 sewage samples collected in 9 Texas cities tested positive for highly pathogenic avian influenza (HPAI). Samples were collected from 10 cities over two months, with 9 cities having at least one positive sample. Tests cannot identify the virus source as coming from animals, humans, or milk. [Confidence: Very High]

These test results indicate that H5N1 has not entered the Canadian dairy cattle population.

The Canadian Food Inspection Agency reported that tests conducted on 142 samples of their commercial milk supply have all tested negative for H5N1. Tests conducted on Canadian dairy cows have also been negative. [Confidence: Very High]

Raw milk sales are rising due to misinformation on H5N1. Businesses should not stock raw milk to avoid liability due to numerous diseases that can be transmitted in unpasteurized milk.

Market research reports weekly sales of raw cow’s milk have increased 21% to 65% compared with the same period a year ago. Some social media influencers are promoting raw milk and making false statements about its safety and health benefits. [Confidence: Very High]

Businesses operating in Michigan should be aware of the new biosecurity protocols and have a plan for implementing them when applicable.

Michigan's biosecurity mitigation strategies aimed at preventing spread of H5N1 among cattle and poultry go into effect today. These practices must be implemented at all dairy farms and commercial poultry operations in Michigan until further notice. [Confidence: Very High]

These test results confirm that the commercial beef supply does not contain H5N1 virus. Businesses should continue to follow food safety protocols when handling and cooking beef. See PHC analysis on 4/26 for more information and guidance on this outbreak.

Tests conducted on beef products by the USDA found no H5N1 avian influenza. The tests were conducted on ground beef sold in grocery stores in areas where dairy cows have tested positive for H5N1. [Confidence: Very High]

Despite widespread media coverage, no new information has emerged. See PHC analysis on 4/26 for earlier assessment. Increased surveillance is likely to identify more human H5N1 cases among dairy workers, but the risk of human-to-human spread still remains low.

The first human case of H5N1 tied to cow-to-human interaction was identified on March 29, soon after H5N1 was found to have infected dairy cows in multiple states. Since then, surveillance of poultry, cows, dairy products, and humans has increased. Investigation has found that multiple dairy workers had illnesses that may have been H5N1 around the time that dairy cows were testing positive, but before human surveillance activities had begun. [Confidence: Very High]

Informational update only. Businesses may want to remind their employees to avoid consuming raw milk or feeding it to their pets as it may contain harmful pathogens.

Over half of the domestic cats on a Texas dairy farm who drank raw milk from cows infected with H5N1 died. The cats became sick one day after symptoms were noted in the cows (March 16/17). Several cats died between March 19–20. Two cats who died were tested for H5N1; both were positive. Cats are known to be susceptible to severe illness from H5N1. [Confidence: Very High]

These test results confirm that the commercial milk supply is safe.

Today, the FDA released the anticipated results from the egg inoculation studies that confirmed pasteurization inactivates H5N1 in dairy products. [Confidence: Very High]

Taiwan's elevation of the travel advisory around H5N1 in Cambodia does not require businesses operating in Taiwan to make any changes, but employees on work travel to Cambodia may have additional questions. As previously noted, employees should avoid live-animal markets and not have contact with or consume diseased poultry.

Cambodia has reported 4 human cases and 1 death related to H5N1 avian influenza A since mid-Jan 2024. All cases had contact with infected poultry. The Ministry of Health & Welfare issued a travel advisory to Cambodia, cautioning against interacting with poultry when visiting the area. H5N1 influenza is typically spread between birds (both domestic and wild) and can occasionally spread from birds to humans, but human-to-human transmission is extremely rare. Viral mutations could increase the potential for human-to-human transmission. [Confidence: Very High]

Informational update only. Businesses may want to remind their employees to avoid consuming raw milk as it may contain harmful pathogens.

Ohio reported that highly pathogenic H5N1 avian influenza (HPAI) was detected in a herd of dairy cattle, the first in this state. The infected cows were from Texas, a state which recently reported HPAI in some livestock, raw milk, and one farmer. The type of H5N1 identified in the cattle is the same that has been causing mass die-offs of birds around the world; it is different from the H5N1 that has caused human fatalities in the past. [Confidence: Very High]

Information update only. Standard industry practice is to cull all birds when Highly Pathogenic Avian Influenza is identified in a commercial flock. The risk of human disease remains low, but avian flu outbreaks in poultry can have a financial impact on businesses in the food industry and can also increase the price of consumer eggs and chicken.

Cal-Maine Foods reported detection of H5N1 avian influenza in a Texas flock, necessitating a temporary halting of egg production. The culled birds represent 3.6% of the company's birds. Eggs that are handled and cooked appropriately are safe to eat. [Confidence: Very High]

Informational update included due to recent H5N1 cases in cattle and a human in Texas. The risk of human disease remains low, but avian flu outbreaks in poultry can have a financial impact on businesses in the food industry and can also increase the price of consumer chicken.

Texas reported avian influenza H5N1 in a commercial poultry flock in a facility owned by the largest US egg producer. This comes just one day after H5N1 was identified in a farmer with exposure to infected cows. H5N1 influenza is typically spread between birds (both domestic and wild) and can occasionally spread from birds to other animals and humans, but human-to-human transmission is extremely rare. The type of H5N1 identified in the Texas poultry is the same that has been causing mass die-offs of birds around the world; it is different from the H5N1 that has caused human fatalities in the past. [Confidence: Very High]

Informational update only. H5N1 has only been identified in dairy cows; beef cows are now being tested. Additionally, H5N1 has been proven to be killed by the cooking process with eggs and poultry; cooking beef is expected to be the same. See PHC analysis on 4/26 for more information and guidance on this outbreak.

The USDA reported that they will conduct tests on beef to identify H5N1 avian influenza. 3 types of tests will be conducted: 1) sampling ground beef in grocery stores, 2) testing muscle tissue from sick cows culled from affected herds, and 3) testing cooked beef inoculated with a virus surrogate to see if it survives. [Confidence: Very High]

Informational update only. Enterprise businesses are not directly affected, but detection of H5N1 in dolphins in North America illustrates that the disease is spreading to new animal groups and to more areas. See PHC analysis on 4/26 for more information and guidance on this outbreak.

Dixie County, Florida reported identification of a dolphin infected with highly pathogenic avian influenza H5N1, the first cetacean with H5N1 in North America. It is not known how the dolphin became infected. Researchers are investigating. Many other species of marine mammals have experienced H5N1-related die-offs. [Confidence: Very High]

Businesses with employees in or traveling to Vietnam should advise them to avoid live-animal markets and not have contact with or consume diseased poultry.

Vietnam has reported a human death from H5N1 avian influenza; this is only Vietnam's second case since 2014. The individual had a history of exposure to wild birds. H5N1 influenza is typically spread between birds (both domestic and wild) and can occasionally spread from birds to humans, but human-to-human transmission is extremely rare. Viral mutations could increase the potential for human-to-human transmission. [Confidence: Very High]

For awareness only. USDA's policy requiring a negative H5N1 test to transport lactating cows goes into effect today. This requirement may detect additional outbreaks outside those in the 9 known impacted states.

The USDA now requires H5N1 testing of all lactating cows being transported across states. All lactating cows must be tested prior to travel, up to 30 cows per herd being transported. [Confidence: Very High]

Informational update only. Enterprise businesses outside the dairy supply chain are not directly affected, but detection in a 9th state demonstrates that the outbreak might be more widespread than is currently known. See PHC analysis on 4/26 for more information and guidance on this outbreak.

The USDA announced that highly pathogenic avian influenza (HPAI) H5N1 has been detected in dairy cows in Colorado, making it the 9th state to identify H5N1 in cows. No additional human H5N1 cases have been identified since the dairy farmer earlier this year; however, H5N1 is not included on standard respiratory panels. [Confidence: Very High]

Businesses in Cambodia should inform their employees to avoid live-animal markets and not have contact with or consume diseased poultry.

A 9 year boy died of H5N1 avian influenza in Kratie province, Cambodia, the first death from avian influenza in Cambodia in 2024. Days later, his brother tested positive, but has been asymptomatic. The boys were exposed by infected poultry at their house; 5 chickens and 3 ducks had died and were cooked for food. Cambodia has been experiencing a resurgence of H5N1 human cases after a decade-long absence of cases. These brothers bring the number of human H5N1 cases in Cambodia in 2024 to four. Risk to the general population from H5N1 remains low, but sporadic cases will likely continue. [Confidence: Very High]

Informational update only. Businesses may want to remind their employees to avoid consuming raw milk as it may contain harmful pathogens.

Texas reported a human case of avian influenza H5N1, the second case in the US since 2022. The case developed conjunctivitis after contact with dairy cows presumed to be infected with avian influenza. H5N1 influenza is typically spread between birds (both domestic and wild) and can occasionally spread from birds to other animals and humans, but human-to-human transmission is extremely rare. The type of H5N1 identified in the cattle is the same that has been causing mass die-offs of birds around the world; it is different from the H5N1 that has caused human fatalities in the past. [Confidence: Very High]

This newly reported case of avian influenza (H5N1) in Cambodia does not require increased respiratory precautions for the general public. Individuals in close contact with poultry should use personal protective equipment.

A Cambodian man who kept backyard chickens has contracted H5N1 influenza. H5N1 influenza is typically spread between birds (both domestic and wild) and can occasionally spread from birds to humans, but human-to-human transmission is extremely rare. Viral mutations could increase the potential for human-to-human transmission.