Could the coronavirus make for a lighter flu season?
Among the many questions confronting public health experts is one that could determine the next turn of the coronavirus pandemic: What happens when COVID-19 meets influenza?
The coronavirus has already killed more than 170,000 Americans in six months. The flu season, which typically runs from October through April, usually leads to tens of thousands of deaths. If both viruses begin sickening Americans simultaneously, that could create what CDC Director Dr. Robert Redfield recently called "the worst fall from a public health perspective that we've ever had."
But in truth, no one knows what is going to happen as fall approaches. It's likely that the flu season will become yet another part of life affected by the pandemic in strange and unexpected ways.
Experts say it's possible that the social distancing measures and widespread closures of businesses in place because of COVID-19 will reduce the spread of the flu so that it's even less prevalent than in a typical season, as appears to have happened in other countries. But they worry that if restrictions ease, this silver lining may not last.
"If things are moving in the correct direction, then we could have reopening, and that might actually coincide with the middle of the flu season — you could actually have increased transmission from that," said Dr. Geoffrey Leung, ambulatory medical director at Riverside University Hospital System. "It really behooves us to do as much as possible to prevent any flu cases we can with the traditional tools."
The reopening of schools in particular could be risky. Though children's susceptibility to serious illness from COVID-19 has seemed relatively low, kids are particularly vulnerable to the flu. The virus runs rampant at schools and then children take it home to their families.
Leung and other experts recommend that people get the flu shot to reduce their chances of falling ill with influenza and to lessen the severity of illness for those who do contract it. They also advise that people stick to the masking and social distancing measures mandated to control COVID-19, because those should also help keep influenza at bay.
"The part that scares me the most is we don't know what the interaction is if one is co-infected by the flu as well as COVID-19," said Dr. Alexander Li, deputy chief medical officer for L.A. Care Health Plan, the nation's largest public health plan. "Having COVID plus flu together is probably bad news."
A handful of studies from China and the U.S. identified patients with influenza and COVID-19, but with mixed results. Some found that the patients seemed sicker than COVID patients without the flu; some found no difference.
If a patient shows up at a hospital with both infections, doctors may not quickly diagnose both illnesses, since they have virtually identical symptoms. If the condition is spotted, there is little known about how to treat such patients. There are medicines that reduce the severity of a flu infection, and medicines that do the same for COVID-19, but the drugs are different and may not mix well.
When the coronavirus pandemic began earlier this year in the United States, the flu season was tapering off. Flu typically peaks in the U.S. in December and January.
But flu season occurs during the Southern Hemisphere's winter, which coincides with summer in the Northern Hemisphere. The experience there typically provides an indication of what kind of flu season might be seen in the north starting in the fall.
But in 2020, there have been virtually no cases of the flu in countries such as Australia and Brazil. Experts say that limited air travel and social distancing measures may have reduced the importation of the disease into those countries as well as its spread within.
There's also some thinking that the coronavirus itself might have kept the flu from gaining a foothold — that only one respiratory virus can dominate at a time. Experts say that phenomenon could theoretically work in both directions, but they wouldn't count on it.
"Usually when one is there, the other isn't — at least that's sort of the dogma," said Dr. James Cherry, an infectious disease specialist at UCLA. "Conceivably, flu could in some way could dampen the coronavirus, but I think this is August and that's several months away, so anything about that will be speculation."
Experts are quick to discourage assumptions that the U.S. will see very little flu just because that was Australia's experience. Australia has also managed to keep its coronavirus death count very low, while the U.S. has not, they point out.
Cherry also warned that some strains of flu could also be more dangerous than others. Researchers recently reported a strain of flu circulating in pigs that could infect humans and cause a pandemic. That would make matters much more complicated — and deadly.