Topline:
The annual flu season usually starts in October or November. But this year, it looks like the flu started to pick up in early September.
Why now: The timing of the flu season isn't the only thing that's odd. It's also unusual that flu activity seems to have started in Western states, such as California, Washington, Hawaii and Alaska, experts say.
The backstory: It's unclear why flu activity would have started so early, and in such an unusual part of the country. But one clue might be a new variant that evolved a mutation, which appears to make it better at evading existing immunity, especially among teenagers.
What's next: Experts suggest scheduling your flu shot.
Fall has only just begun, but it's already time to start thinking about the quintessential winter bug: the flu.
The annual flu season usually starts in October or November. But this year, it looks like the flu started to pick up in early September.
"There are enough signs pointing in the same direction to make me think, 'OK, yes. This is the start of flu season,'" says Caitlin Rivers, an epidemiologist at the Johns Hopkins Bloomberg School of Public Health.
The percentage of people testing positive for the flu in the West has been rising steadily since around the beginning of September, she says. And the number of people showing up in emergency departments because of the flu has also been rising for weeks, she adds.
"It's very uncommon to see flu activity rising this early. It's activity that we might normally see more like November or December," she says.
The timing of the flu season isn't the only thing that's odd. It's also unusual that flu activity seems to have started in Western states, such as California, Washington, Hawaii and Alaska.
"It typically starts in the South and then expands from there," Rivers says. "So two uncommon developments there."
Rivers stresses that the amount of flu activity is still very low in most parts of the country. But that's starting to change as the flu picks up nationwide.
It's unclear why flu activity would have started so early, and in such an unusual part of the country. But one clue might be a new variant that evolved a mutation, which appears to make it better at evading existing immunity, especially among teenagers.
"That's our best argument for what's going on right now in terms of this early flu season," says Dr. Alex Greninger, a virologist who heads infectious disease diagnostics at the University of Washington. Doctors there are seeing as much flu right now as they usually would around Christmas, and the mutated variant appears to be common, he says.
So Greninger, Rivers and others are urging people to think about getting their flu shot earlier than usual.
"It's crucial that people get an influenza vaccine," says Scott Hensley, a virologist at the University of Pennsylvania. "And this might be a year that people might want to get a vaccine early."
But the Centers for Disease Control and Prevention hasn't been promoting flu shots as it usually does. Health Secretary Robert F. Kennedy Jr., who oversees the CDC, is a long-time vaccine skeptic.
"It is disappointing that CDC is quiet given that flu kills of hundreds of kids a year and can result in tens of thousands of hospitalizations and tens of thousands of deaths," says Dr. Demetre Daskalakis, who resigned last year as the director of the National Center for Immunization and Respiratory Diseases at the Centers for Disease Control and Prevention to protest what he called political interference at the agency.
The CDC declined to make an official available to NPR for this story. In a statement, a CDC spokesperson said, "CDC is developing a communications strategy to provide clear, accessible information about influenza vaccination and other critical steps people can take to protect themselves during respiratory virus season. This includes information about the benefits and risks of vaccination to support informed decision-making."
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