Experts predict this year's flu season to be worse than usual—here's why
Based on how flu spread in the Southern Hemisphere, we may be in for some pain.
Every year, flu season in North America starts to peak around the holiday season. But this year, doctors and researchers are especially worried.
“We will have a significant flu season this year, and we have a lot of concern that it's going to be more severe than typical,” says Richard Martinello, an infectious diseases specialist and chief medical officer at Yale Medicine.
Why? The version of the virus that’s circulating around the globe has undergone significant genetic changes that make it easier to infect people, and therefore to spread between them. It means “our antibodies won’t see it as well,” says Danuta Skowronski, a physician-epidemiologist and flu researcher at the British Columbia Centre for Disease Control, who first flagged the mutations in the Journal of the Association of Medical Microbiology and Infectious Disease Canada in October. What’s worse, these genetic changes happened too late to account for in flu shot formulations.
Flu rates have already begun ticking up in the U.S. As of late November, respiratory illnesses (which includes colds and COVID-19) comprised some five percent of doctor visits, up from three a week earlier. Because these viruses are extremely contagious, once rates start rising, they can quickly spike.
(Don't risk your holiday plans: The basics still matter for COVID and flu.)
But while this year’s vaccine is not a perfect match for the dominant strain, experts emphasize that it’s still important to get the shot, as well as to take other steps to combat the freight-train of flu likely heading our way.
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Concerns about the new mutations started to emerge this summer, which is winter—and thus prime flu season—in the Southern Hemisphere. Australian experienced a record-breaking number of cases, while Brazil saw a 127 percent increase in severe flu.
Flu viruses tend mutate more than other viruses because their genes are grouped in segments instead of one long string. Any segment can easily swap genes with other viruses to give itself additional advantages. This year, three alterations in pivotal spots as well as three additional changes make the virus less visible to our immune system, allowing it to more easily burrow into the cells to make us sick.
Eventually, this version, dubbed subclade K, circles the globe. “There's a ping-pong effect between Northern and Southern Hemisphere flu seasons,” says Marcus Pereira, an infectious diseases physician who specializes in immunocompromised patients at New York’s Columbia University Irving Medical Center. “Whatever is there eventually makes it way up to us, and vice versa.”
This version of the virus is so effective at infecting people it’s already caused an unprecedented, outbreak in the United Kingdom, months earlier than usual.
It is predicted to dominate in the U.S. and Canada during the holidays, a time when travel and family gatherings typically swell flu exposure.
The vaccine is mismatched. That makes it even more important to get.
As is typical, vaccine components were set last winter by the World Health Organization for a September rollout in the U.S. This requires a bit of guessing as to what might circulate months later, especially regarding the fast-mutating influenza A virus (which underwent the concerning genetic changes).
This year, the targets are significantly off. A score of three in so-called “antigenic difference” is considered a mismatch; this has a distance closer to six, the Canadian journal article noted.
Counteractively, experts say, it’s even more important to get the flu shot this year, because the more contagious virus will infect a larger pool of people, increasing the number who get very sick. Even vaccines with lower effectiveness keep thousands of people out of doctors’ offices and hospitals by reducing disease severity, Martinello notes. The vaccines also target the less-malleable influenza B, which sometimes surges later in a season.
In the Southern Hemisphere, people who got a flu shot this summer had nearly 50 percent fewer hospitalizations, according to an analysis by the U.S. Centers for Disease Control and Prevention. But whether the U.S. and Canada will fare the same, or worse, won’t be known until at least mid-January, when more people will be exposed and most who want the shot have gotten it, Skowronski says.
So far, just 36 percent of U.S. children have been vaccinated—down 23 percent from a half-decade earlier, likely due to increased vaccine skepticism. Only 13 percent of people over 65, a group at high risk for flu hospitalizations and death, have done so.
Other important actions to minimize flu’s spread include staying home when you have respiratory symptoms, even if you’re convinced it’s just a cold. In the thick of flu season, “it's not unusual for upwards of 50 percent of people with symptoms limited to runny nose, sore throat, and maybe a dry cough to actually have flu,” Martinello says, noting the people you pass it to may develop a more serious condition. If you must be around others, wear a well-fitting mask and sneeze into your elbow, not your hands.
Fortunately, the mutations don’t diminish prescription antiviral drugs’ effectiveness, so contact your doctor as soon as you feel ill—within 12 hours for optimized results but with 48 hours for them to work at all, Skowronski says.
(Here’s how different cold and flu drugs work.)
People at especially high risk for hospitalization and death—those with compromised immune systems from disease or medications, pregnant women, seniors over 65, and young children—should be especially cautious this flu season.
But even if you’re not among this group, getting vaccinated helps to minimize their exposure. “In some ways it’s the responsible thing to do,” Pereira says. “You’re taking the vaccine to protect yourself, but also to protect the vulnerable people you love.”
