If you suffered and recovered from COVID in the past few years, you might wonder if it increases your risk of other infections. Patients are asking their physicians and other health care providers this question a lot lately.
Last winter’s flu season arrived early in the United States, did COVID play a part in its timing? Respiratory Syncytial Virus (RSV) led to record numbers of hospitalizations of children last winter, and Streptococcal infections surged in the United Kingdom, U.S., and elsewhere. People want to know if there’s a link between COVID and these other diseases.
COVID is linked to some subsequent infections, but we need to learn a great deal more about the relationships between COVID and others. Here is what we know about various infections that can follow or arise during COVID:
Bacterial Pneumonia & Superinfections
The link between COVID illness and later infections is well established for bacterial pneumonia arising during an acute COVID viral illness. Healthcare workers call this phenomenon a “superinfection.”
Superinfections are common with COVID infections. In hospitals, physicians regularly confirm bacterial pneumonia in the days and weeks following an admission for COVID disease. Patients then require antibiotics to treat these secondary infections.
COVID isn’t the only illness with links to superinfections. Influenza or RSV often create an environment for additional infections. A large percentage of deaths during the infamous 1918 influenza pandemic were from Strep pneumonia that arose days after the initial influenza viral infection. In 1918, antibiotics were not available, so many who made it through the influenza virus onslaught then did not survive the secondary bacterial superinfection.
Influenza and RSV
Last winter’s flu season arrived months early in the U.S., catching many by surprise and infecting many before vaccines were widely deployed. Around the same time, RSV, which causes “croup” and related respiratory illness in children, was filling pediatric units in hospitals in the U.S. and elsewhere. RSV has the potential to be fatal in children and in the elderly, who were also impacted.
These events drove the question – Did COVID make us more susceptible to these ailments by impairing our immune function, since so many who got flu or RSV had just had COVID, which has known immune system impacts?
Another question centered on what is known as “immune debt.” COVID lockdowns kept us from catching flu or RSV, so our immune responses were not as primed to respond to flu and RSV as they would have been if we’d been getting regularly exposed to those germs. Did our resulting immune debt then lead to the unusual waves of these illnesses? Evidence suggests that answers to this question point towards both decreased overall immune function and germ-specific immune debt playing roles in this past winter’s flu and RSV surges.
Influenza typically spikes in the winter months in the U.S., and its timing and intensity vary a lot from year to year, so it is possible that last winter’s early flu surge was due purely to chance. Prior to the COVID lockdowns, however, RSV infected almost everyone by the time they were two years old, providing immunity to most children. During the COVID lockdowns, however, infants had little exposure to others and tended not to get infected with RSV. Last winter, therefore, the number of unexposed and non-immune infants in the U.S. was larger than usual. It is generally accepted that a portion of last winter’s RSV surge was due to those previously uninfected children catching RSV for the first time, as an unintended consequence of COVID lockdowns.
Fungi
The number of cases involving a new type of difficult-to-treat fungal infection, Candida auris, has nearly doubled in 2021 compared to 2020 to just under 1,500 cases in the U.S. Persons with severe COVID requiring hospitalization had very high rates of Candida auris compared to others. It is not known if the COVID itself predisposed them to acquiring that fungus, whether medicines used to treat COVID were linked to Candida auris onset, or whether just being in the hospital and sick was the driver.
Common Bacterial Infections
Clinicians are describing increases in common bacterial infectious diseases, including but not limited to Staph and sexually transmitted infections. Staph infections of the skin, blood and heart are increasing in number. Meanwhile, some sexually transmitted infections in the U.S., like syphilis and chlamydia, have reached levels not seen in decades. Additionally, the CDC has reported increases in brain abscesses in children during the last year.
Severe Strep Infections
This past year has also been characterized by documented increases in certain kinds of severe Strep infections. In the U.S., U.K., and in many European countries, there have been increases in “invasive” Strep infections for children under 10 years of age, that cause dangerous diseases like bloodstream infections, meningitis and flesh-eating bacteria syndromes. Right now the higher rates of invasive Strep infections are only associated with the COVID pandemic, and COVID has not been shown to be causal of the Strep surges. Nevertheless, the magnitude of the increases and number of countries reporting them is notable, leading to speculation about a link. Plus there is precedent for respiratory viral infections leading to increased Strep susceptibility, namely the 1918 flu pandemic noted above.
As researchers try to clarify the links between COVID and later infections like Strep, lab studies play a key role. From those studies, it is clear that some immune system cells (for example, CD8+ T cells) and the infection-fighting products they release are altered during and after COVID, in ways that can increase infection susceptibility. There are altered quantities of some immune system cells and their products after COVID, as well as differences in how well those cells function. A recent NIH press release noted that some of the COVID-related damage to our immune system cells leads to states of impaired immune protection, analogous to what is seen with HIV or hepatitis C disease.
In sum, while susceptibility to infection for any one person is influenced by many factors, we are seeing patterns emerge and lab studies result that suggest COVID increases subsequent infection susceptibility, for some people, from some infections, for some amount of time. The magnitude of that influence likely varies widely from person to person. Further clarifying this matter is a priority, as we expect continued COVID presence for the foreseeable future..
