Experts warn that a COVID-flu 'twindemic' might hit hospitals hard this year

Experts keeping an eye on COVID-19 worry that the somewhat comforting assessment given the public when vaccines arrived—that they will keep people from dying or being hospitalized—might not hold up, at least the part about being hospitalized, if we’re hit with a fall and winter surge yet again. Hospitalizations might indeed rise, taxing an already overburdened and understaffed healthcare system especially if influenza makes a comeback.

In terms of what COVID-19 might do, several factors must be accounted for: the rise of new variants that seem to be able to evade antibodies produced by vaccines or former infection, the intermingling of people indoors as they did in pre-pandemic days, and indications that immunity may be waning.

Nobody expects COVID-19 to be the killer it was in 2020 and 2021. However, during those surges, healthcare workers feared having to battle a twindemic: COVID-19 and influenza at the same time. Luckily, that didn’t happen.

In fact, cases of influenza sunk to historic lows, according to the Centers for Disease Control and Prevention (CDC), a development that many experts considered a byproduct of mitigation measures—social distancing, hand hygiene, and, particularly, masking—against COVID-19. What people did to avoid COVID-19 stopped the flu in its tracks.

“Since SARS-CoV-2 emerged in the United States in early 2020, influenza activity has been lower than that seen before the pandemic,” said a study in Morbidity and Mortality Weekly Report, a CDC publication. “The adoption of COVID-19-related mitigation measures might have had an impact on the timing or severity of influenza activity.”

This year the twindemic might hit partly because people don’t wear masks anymore, but also because people might have gotten lax about getting the flu vaccine, ignoring the urgings of organizations like American Hospital Association to get inoculated.

William Schaffner, M.D., medical director of the National Foundation for Infectious Diseases (NFID), explained the situation recently to JAMA Network. From the article: “Given the low severity of the last two flu seasons, ‘[w]e really have to remind people about influenza and how it’s so important,’ Schaffner said. ‘The sense I have is that we vaccinated less than our targets.’”

An NFID survey states that while 69% of adults in the U.S. agree that flu vaccination is the best preventive measure against flu-related deaths and hospitalizations, only 49% plan to get a flu vaccine during the 2022-2023 flu season. Meanwhile, individuals should be careful when it comes to selecting a mask. About 60% of KN95 masks evaluated in 2020 and 2021 did not meet safety standards, according to the CDC.    

Richard Webby, PhD, of St. Jude Children’s Research Hospital in Memphis, told JAMA Network: “I do think we’re likely going to have a big flu season.”

Also, predictions of how troublesome influenza might be in the Northern Hemisphere are based on how it’s been in the Southern Hemisphere, where flu season occurs from April to September and Australia experienced a higher number of flu cases this year than it has in any of the previous five years.

Justin Lessler, an infectious-disease epidemiologist at the University of North Carolina at Chapel Hill, told Nature that “in a bad flu year hospital systems get pretty stressed.” Nature reported that “even a relatively muted COVID-19 wave” together with a fulsome influenza surge will place a heavy burden on hospitals. 

One of the experts who cited the Australian flu numbers is Anthony Fauci, M.D., the director of the National Institute of Allergy and Infectious Diseases and President Biden’s chief medical advisor.

In an interview for the USC Annenberg Center for Health Journalism yesterday, Fauci said that “we are entering into the winter months where no matter what the respiratory disease is, there’s always the risk of an uptick in respiratory diseases.” Fauci added that “even though BA.5 is the variant that is the one that is dominant, you have the creeping up of variants that are sub-linages like BA.4.6. We don’t have much of BA.2.75.2 yet, but there are other countries that do have that. Although we can feel good that we are going in the right direction, we can’t let our guard down.”

The countries that have seen an uptick in COVID-19 cases include the United Kingdom, where the number of people testing positive for the infection has been rising steeply the last two weeks, according to the U.K.s Office of National Statistics. Part of that surge is because of the rapid growth of BQ.1, a subvariant of BA.5.

A twindemic is far from inevitable. In fact, we may not get hit with a twindemic because of the way Omicron and influenza interact. In the JAMA Network article, Schaffner posits: “Do these viruses influence each other’s behavior? Do they sort of interfere with each other?”

And even Webby, who thinks we’re probably in for a tough flu season, seems to hedge his bets. He tells JAMA Network that the Omicron variant “really blunted the flu season for reasons we don’t understand.” It’s possible that when “you get infected with a virus you get this sort of nonspecific immunity.”