The flu has not only been out of mind, it’s been largely out of sight. Between late September 2020 and August 2021, there were only a little over 2,000 lab-confirmed cases of influenza in the United States, according to the Centers for Disease Control and Prevention (CDC). In a typical flu season, the United States sees more than 200,000 lab-confirmed cases in that time frame, a tiny fraction of the actual number of cases; in the 2019–2020 season, actual cases were estimated at 38 million, says the CDC. Flu-related hospitalizations were also the lowest on record in 2020–2021. And, there was only one infant death from the flu, compared with 199 the previous season, the CDC reports. While that’s all positive news, last year’s hiatus from the flu has many experts concerned about what this next year might bring — for the flu, as well as other respiratory viruses, says Chloe Bryson-Cahn, MD, the associate medical director of infection prevention at Harborview Medical Center in Seattle. “With the caveat that flu surprises us every year and no flu season is exactly like the one before it, this winter could be much worse than previous years if we’re battling COVID-19, a huge flu season, and a big RSV [respiratory syncytial virus] season,” she says. “I think it could really cause a lot of turmoil in our hospitals, our places of work, and schools.” RELATED: Is It a Cold, the Flu, or COVID-19?
Positive Lessons From Last Year’s Flu Season
Experts believe last year’s low level of flu transmission was largely due to the protective measures many people took to reduce the spread of COVID-19. “I think one thing we have learned as a result of the pandemic is that we really have the ability to impact the way influenza is transmitted in our community,” says Dr. Bryson-Cahn. “Vaccination, masking, distancing, staying home from work when we are sick, keeping children home from school when they are sick, folks washing their hands — all these things that we recommend to help reduce the spread of COVID-19 also help prevent illness and death from influenza,” she explains. Indeed, many infectious disease experts see the mild flu season as the silver lining of the COVID-19 pandemic. “Every year we have people in our hospital die of the flu, especially young children and pregnant women, but last year we didn’t — no one died in our hospital due to the flu,” says Bryson-Cahn. “That was an amazing thing, and it gives me a lot of hope for the future about how we can control this infection.”
Why We May Be More Vulnerable to the Flu This Year
As COVID-19 vaccination — combined with pandemic fatigue — leads to less masking and social distancing, and as more people return to work and school this fall, the flu will likely come back. And many experts fear it may come back with a vengeance. While the historically low levels of flu may have spared us from a “twindemic" — a strong flu season hitting amid an ongoing COVID-19 outbreak — the lack of exposure to the flu could also make the population more susceptible to the virus when it returns. “Even in years when you don’t catch the flu, you are still often exposed to it,” says Eili Klein, PhD, an associate professor of emergency medicine at Johns Hopkins Medicine in Baltimore, and a fellow at the Center for Disease Dynamics, Economics, and Policy in Washington, DC. “That exposure helps your immune system make antibodies that ‘remember’ the virus and how to attack it.” This year, most of us won’t have the boost. “Because there was little flu virus activity last season, adult immunity (especially among those who were not vaccinated last season) will now depend on exposure to viruses two or more seasons earlier,” says Dr. Klein. Older adults may be especially vulnerable because their viral antibodies tend to wane faster. “That’s why older people are more likely to get the flu — their immune system doesn’t work as well,” says Klein. Children could be at a higher risk as well, says Ali Mokdad, PhD, a professor of global health at the University of Washington’s Institute for Health Metrics and Evaluation in Seattle. “Many of our children under the age of two have never been exposed to the flu because they’ve stayed home throughout the pandemic. Now they’re going back to day care and they will likely be exposed,” he explains. Even healthy adults may be affected by lack of exposure. “It will take a little longer for our immune system to recognize the virus,” says Dr. Mokdad. “That delayed response coupled with few existing antibodies could mean you have two or three days extra of flu symptoms.” RELATED: Summer Colds Are Making a Comeback
Flu May Follow in the Footsteps of Other Viruses Now on the Upswing
In recent months, we’ve already seen the impact that lack of exposure to a virus can have once COVID-19 restrictions are loosened. When many of us shed our masks after getting vaccinated for COVID-19, for example, we saw a big uptick in summer colds, says Kline. The respiratory syncytial virus, known as RSV, has also seized the opportunity to spread. Last June, the CDC issued a health advisory that warned of a surge in RSV infections across southern states like Alabama, Florida, Mississippi, and Texas. Hospitals in the Midwest also reported an increase in cases. RSV causes cold-like symptoms, such as runny nose, coughing, sneezing, wheezing, a decrease in appetite, and a fever. Although RSV is usually mild, it can be serious for infants and older adults. According to the advisory, older infants and toddlers may now be at increased risk of severe RSV-associated illness as a result of reduced exposure during the pandemic. “There have been children admitted to the hospitals due to RSV in many places such as New Zealand and Australia,” says Mokdad. “And, this summer we’re seeing more kids with RSV in our hospitals.” The fact that this respiratory virus is circulating in the United States many months earlier than normal is something Mokdad finds concerning. RELATED: RSV Infections: Why the Surge?
Last Year’s Mild Flu Season Makes This Season’s Harder to Predict
Last season’s low number of flu cases is causing another potential wrinkle: Experts have less information to use for predicting what this year’s flu season might be like and what strains may be circulating, says Bryson-Cahn. Each year the World Health Organization (WHO) determines which viruses will be included in the flu vaccine in the Northern Hemisphere on the basis of which viruses have been circulating in the past two or three years, as well as what is circulating in the Southern Hemisphere earlier in the current flu season. Public health officials don’t have much to go on this year. And, so far, there isn’t much flu in circulation globally. According to the WHO’s August 2021 influenza update, global flu activity has remained at lower than expected levels for this time of year, which they believe may be due to continued COVID-19 measures like physical distancing and masking. But there have been some outbreaks of the flu in the Southern Hemisphere, says Mokdad, who believes that scientists have had enough information to build an effective flu shot. “This virus isn’t going to mutate outside what we expected.” Indeed, with fewer circulating strains of the flu, there is less chance for the virus to mutate, he notes, which could potentially translate into a more effective vaccine — at least at the start of the flu season. “All bets are off when the flu begins circulating among people who have not been exposed and among people who are likely more susceptible,” says Mokdad. “These factors will mean the virus can mutate faster.”
Consider Getting Your Flu Shot Early — and Masking in High-Risk Situations
The CDC recommends that virtually everyone six months and older get a flu shot. And, right now, they are recommending people get vaccinated by the end of October. Klein seconds this advice. “Given there will be a greater number of susceptible people coupled with kids going back to school, it could mean that the flu may peak earlier this year,” he says. “I wouldn’t recommend waiting until late November to get the flu shot.” Keep in mind that it takes about two weeks after getting the shot for antibodies to develop and provide protection against the flu. Children who need two doses of vaccine to be protected should start the vaccination process sooner, because the two doses must be given at least four weeks apart, recommends the CDC. Other ways to ward off flu: Avoid close contact with people who are sick, wash your hands frequently, and don’t touch your eyes, nose, or mouth. And, even once you’ve gotten both your flu and COVID-19 shots, it can still be wise to wear a mask in high-risk situations. Because of the surge of the more contagious COVID-19 delta variant, the CDC now recommends that even people who have received the COVID-19 vaccine wear masks indoors in public if they live in an area of substantial or high transmission. “It is somewhat concerning that our public health organizations are urging people to put their masks on again, and [yet] I’m not seeing people doing that in the same way they did a year and a half ago,” says Bryson-Cahn. Although it’s understandable that people are tired of masking and social distancing, she stresses that now, when delta is taking over our region and other viruses like the flu may start gaining a foothold, is the wrong time to lose steam. “We are seeing breakthrough infections among vaccinated people, and there continues to be a significant amount of unvaccinated people who are at great risk,” she explains. Masking and social distancing work, stresses Bryson-Cahn, both for reducing transmission of COVID-19, and also (as we saw so clearly last year) for significantly reducing illness, hospitalizations, and deaths related to the flu.
