Perhaps the oddest consolation prize of America’s crushing, protracted battle with the coronavirus is the knowledge that flu season, as we’ve long known it, does not have to exist.
It’s easy to think of the flu as an immutable fact of winter life, more inconvenience than calamity. But each year, on average, it sickens roughly 30 million Americans and kills more than 30,000 (though the numbers vary widely season to season). The elderly, the poor, and people of color are all overrepresented among the casualties. By some estimates, the disease’s annual economic cost amounts to nearly $90 billion. We accept this, when we think about it at all, as the way things are.
Except that this past year, things were different: During the 2020–21 flu season, the United States recorded only about 2,000 cases, 17,000 times fewer than the 35 million it recorded the season before. That season, the flu killed 199 children; this past season, as far as we know, it killed one.
“We’ve looked for flu in communities and doctors’ offices and hospitals, and we’ve gotten almost zero,” says Emily Martin, a University of Michigan epidemiologist who’s part of the CDC’s flu-monitoring network. The same was true of other seasonal respiratory viruses last winter, says Saskia Popescu, an epidemiologist at George Mason University in Virginia, though some have since rebounded. RSV, parainfluenza, rhinovirus, adenovirus—for a while, they all but vanished.
[Read: The pandemic broke the flu]
For this, perversely, we can thank the pandemic. The coronavirus itself may have played some role—infection could produce a general immune response that would also confer protection against the flu—but most of the epidemiologists I spoke with instead emphasized the importance of the behavioral changes adopted to slow the spread of the coronavirus: masking, distancing, remote learning, working from home, limiting indoor social gatherings. Despite the inconsistency with which America deployed them, these measures helped tamp down the spread of the virus, but they completely crushed influenza, a less transmissible foe to which the population has considerable preexisting immunity. We set out to flatten the curve, and we ended up stamping out the flu.
This was one of the few blessings in an otherwise abysmal winter, in which COVID cases and deaths surged to their highest levels ever in the U.S. At least we didn’t face the dreaded “twindemic.” But our triumph over the flu also poses a dilemma, as much ethical as epidemiological. We’ve demonstrated conclusively that saving nearly everyone who dies of the flu is within our power. To do nothing now—to return to the roughly 30,000-deaths-a-year status quo without even trying to save some of those lives—would seem irresponsible. So what do we do? Which measures do we maintain and which do we let go?
One thing we’re not going to do is go into lockdown every year (or even go into what passed for lockdown in the United States, which in reality was not). This, the public-health experts I spoke with for this story all agreed, would be neither feasible nor desirable. Broad restrictions on travel and large indoor gatherings, they said, also seem like nonstarters (though Seema Lakdawala, a flu-transmission expert at the University of Pittsburgh, suggested that companies might consider rescheduling their annual holiday party for the summer and moving it outdoors). Even more moderate capacity limitations, though beneficial from a health perspective, Popescu told me, are “tricky for business.”
Still, perhaps other, targeted versions of the restrictions deployed during the pandemic could work. Linsey Marr, an environmental engineer at Virginia Tech, proposed a sort of “circuit breaker” system, in which schools and workplaces could go remote for a week or two to slow flu transmission during severe local outbreaks. Before shutdowns kick in, people could keep a close eye on flu cases in their area—just as many have monitored COVID numbers over the past two years—and make their own personal risk assessments. For one person, Lakdawala imagines, that might mean being more efficient in a crowded grocery store; for another, masking at a movie theater. (That said, people tend to be less than perfect at gauging the danger of different situations.)
Masks, in theory, are one of the simplest pandemic-times interventions to hold on to. They are “the low-hanging fruit,” says the Emory University immunologist Anice Lowen, because, unlike shutdowns or restrictions on indoor gatherings, they don’t disrupt our daily routines. In an ideal world, several epidemiologists told me, people would mask in crowded indoor spaces during flu season—if not all the time, then at least when case counts are on the rise. If that became the norm, Marr told me, “we would see huge reductions in colds and flus. No question.”
[Read: Why are Americans still—still!—wearing cloth masks?]
Ours, of course, is not an ideal world, and masking is unlikely to become an uncontroversial American norm anytime soon. Demand too much, warns Angela Rasmussen, a virologist at the Vaccine and Infectious Disease Organization, in Saskatchewan, Canada, and you risk inciting backlash. Even if health officials ask people to mask only during local surges, she worries, “you’re going to have a lot of people who are like, ‘Well, we saw this coming. First you mandated masks for COVID; now you’re mandating masks all the time. It’s all about control! What about my freedom?’”
At the very least, both Marr and Rasmussen would like to see the CDC recommend that people wear masks when symptomatic and provide information about how masking in crowded indoor spaces can lower the risk of infection. For now, the CDC isn’t prepared to endorse any new antiflu interventions. David Wentworth, the virology, surveillance, and diagnosis chief within the agency’s influenza division, agrees that pandemic precautions played a major role in reducing flu transmission over the past year. But he told me that the agency needs to see more data on which measures were most effective before it officially recommends any of them. “It sounds like we’re doing nothing, but really we want to understand what factors have the big impact before you start making those kinds of recommendations,” he said. “It’s not that we don’t care about the tens of thousands of people who are impacted by flu.”
The agency’s most up-to-date information on masks and the flu is labeled “Interim Guidance” … as it has been since it was published in 2004. It stresses, as several of the experts I spoke with did, that no one intervention can provide total protection, and it even mentions social distancing and school closures as possible “community measures.” But outside of a health-care setting, it recommends masks only for people who either are diagnosed with the flu by a doctor or have a fever and respiratory symptoms during a known local outbreak—and even then, it stops short of an actual prescription. Those people should try to stay home, it says, but if they can’t, “consideration should be given” to masking in public spaces.
Like everyone else I spoke with, Wentworth strongly recommended flu shots, which he called “the most important tool” at our disposal for fighting influenza. And while most years’ flu shots are considerably less effective than the best-performing COVID vaccines, several of the experts I spoke with said that not-so-far-off advances in immunization technology could narrow the gap before long.
[Read: The most important vaccine I’ll get this fall]
Certainly, methods for knocking out the flu need not be limited to successful pandemic interventions. Many experts advocated for changes they said were long overdue even before the pandemic began, chief among them paid sick leave, which every wealthy country in the world except the U.S guarantees. As a result, nearly a quarter of the American labor force must report to work when ill. Among the bottom quartile of earners, that proportion is more than half. And while many employers have introduced more accommodating policies during the pandemic, there’s no guarantee they’ll outlast it. In schools, perfect-attendance awards encourage a similar dynamic, even if well intentioned, says Sarah Cobey, an evolutionary biologist at the University of Chicago.
Giving workers and students the ability to stay home when sick would go a long way toward reducing the flu’s spread. But policy changes alone won’t unravel the problem overnight. “There’s a real culture … that if you’re not on your deathbed or you’re not going to the hospital, that you’re fine to go to work,” Rasmussen told me. “If you’re sick, you should stay home. It seems like a no-brainer, but people are actually really resistant to that.”
Whether because of that culture or because they don’t realize they’re contagious, some sick people will still come in to work. That, experts told me, is where overhauled ventilation can help us. For all the advances we’ve made in preventing diseases transmitted via water or insects, my colleague Sarah Zhang has written, we have overlooked air. Until the advent of sewer systems and water treatment, Marr said, people accepted deadly waterborne diseases as a basic fact of life. These days, the idea of drinking dirty water strikes most as repulsive, even as we resign ourselves to breathing filthy air and contracting seasonal respiratory viruses. But now, Marr said, “we’ve seen we don’t have to live that way.” By better ventilating our buildings—which to this point have largely been optimized for energy efficiency, not air quality—she said, we could do for air what we have done for water.
That is at least a little ways off, though. To fight the flu right now, flu shots and nonpharmaceutical interventions are all we’ve got. If we’re going to save people, that’s how. We’re unlikely to consistently replicate the nonexistent flu season we just had, but the experts I spoke with said that even the more modest precautions could reduce mortality by 25, 50, even 75 percent, which translates to tens of thousands of lives saved. Those figures, they stressed, are highly speculative. So far, the 2021–22 season is off to a good start, though some experts worry that the flu will be back with a vengeance before long.
Whatever happens, there can be no more illusions of inevitability. The flu, it turns out, has always been a choice. Now we have the opportunity to do something about it—and the burden of knowing we can.
