IThe flu arrived early this year, appearing on the West Coast “about two and a half months earlier than normal,” says Dr. Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota — a timeline not seen since the 2010 season.
And while the Centers for Disease Control (CDC) still considers flu activity low overall, with 16,000 flu-related hospitalizations recorded so far, it expects infections to continue to rise in the coming weeks as the virus spreads across the Midwest and East Coast.
Although factors such as travel habits may have contributed to this early season, “there is no completely compelling explanation for why this happened,” notes Dr. Amesh Adalja, an infectious disease specialist at the Johns Hopkins Center for Health Security.
The timing isn’t the only unusual thing about this year’s flu – here’s what you need to know.
What’s different about this year’s flu: a mutated H1N1 virus
The dominant flu strain this year is an H1N1 virus carrying a mutation known as G155E. According to Adalja, there is no evidence that the mutation makes the virus more likely to cause severe illness, although it resembles the characteristics of H1N1 strains that circulated before 2009.
Early research suggests that adolescents and young adults under 25 “have less immunity” to this strain, Adalja says — the virus may be “more able to evade some of the immunity that people have from previous infections and vaccinations,” he says.
So far this season, one death associated with pediatric influenza in the United States has been reported, that of an elementary-aged child traveling from outside the Denver metro area. An estimated 24,000 people, including 198 children, died from flu-related illnesses during the 2025-2026 season.
According to Dr. Alex L Greninger, chief of the division of infectious disease diagnostics at the University of Washington, differences in how people respond to the flu have more to do with who is infected — people with diminished cardiorespiratory fitness, for example — than with the virus itself. “If you’ve recently had heart disease, when the flu hits, it can put a strain on your heart and lung function,” he says.
The vaccine was developed before this mutation – but it’s still worth it
Every February, the World Health Organization (WHO) brings together experts who review global flu data and create an informed, but not entirely certain, forecast on the three flu variants they expect to see dominate the Northern Hemisphere over the coming winter.
“We make flu vaccines the same way as in the 1940s; we use very old technologies that require long production times,” explains Adalja.
This year, their predictions were wrong. “This particular variant really emerged after we had already chosen the content of the vaccine,” Osterholm notes, meaning this year’s vaccine is less effective against infection.
But, Osterholm says, the question is not whether the vaccine works or not, but whether it is less protective. Being vaccinated is like “having your seat belt on against the flu. It protects you against serious illness, hospitalization and death.”
The poor match between the vaccine and this year’s flu is not linked to the United States’ exit from the WHO. “Even though the United States left the WHO, which is a bad decision for a number of reasons, the CDC participated in the WHO strain selection process,” says Adalja. “So it wasn’t like they weren’t part of that decision-making process… The strains used in the northern hemisphere and administered in the United States are identical to those administered in Canada and Mexico, for example.”
This is the first year that an mRNA-based flu vaccine, developed by Moderna, has also been available to the public. Called mFlusiva, the vaccine is recommended for adults 50 and older, a group that is at highest risk for influenza, and has been shown to produce milder reactions than mRNA Covid vaccines, Osterholm says.
Although mFlusiva was also developed before the flu mutation, Adalja hopes that mRNA technology will help future vaccine strain selections move closer to the start of the flu season, improving the quality of the match.
When should you get vaccinated this year?
Since it takes about two weeks after getting a vaccine for your body to create enough antibodies to protect you, the time is close to protect yourself before the holidays.
“Now is the time to get vaccinated,” says Osterholm. “People under 25 in particular should be encouraged to get vaccinated earlier than usual, which is now. »
Osterholm encourages everyone to get both the Covid and flu shots, saying he received his the same day. It’s “not unexpected” to feel sore for a day or two after your injections, he says. “Just know that it’s much better to have a reaction than to get the flu.”
If you become ill, at-home antigen tests for influenza, influenza A, influenza B, and respiratory syncytial virus are all available. Experts agree that testing is worth it because knowing your strain can help your doctor prescribe helpful antiviral medications like Tamiflu or Xofluza, which can reduce serious illness, hospitalizations and recovery time.
If you become ill, it is important to stay home to mitigate the spread of flu and protect vulnerable people; If you must leave your home, Osterholm recommends wearing an N95 mask.
Where can you find reliable advice about the flu?
While once people could find reliable information about the flu vaccine on the CDC website, this year it’s a little more complicated. In 2025, Health Secretary Robert F Kennedy Jr fired all members of the CDC’s vaccine advisory committee and appointed his own picks. A federal court has since suspended the new panel’s votes. As a result, the systems that normally advise Americans are at a standstill, with the CDC relying on last year’s flu recommendations.
“There is no (Advisory Committee on Immunization Practices). It doesn’t exist in a sense,” Osterholm says.
Other major medical groups have stepped in to provide reliable information to the public. In September, the American Academy of Pediatrics, the American Academy of Family Physicians, the American College of Obstetricians and Gynecologists, and the Infectious Diseases Society of America released coordinated recommendations. They relied on a review of the evidence by the Vaccine Integrity Project, an initiative of the Osterholm Research Center. All four groups advise the flu vaccine for everyone six months and older, including people who are pregnant in any trimester.
Adalja advises people to start with these groups rather than the CDC. “Some CDC data is valid and reliable, but other data is not,” he says. To a layman, “it’s hard to know if this is something that was tainted by RFK Jr.”
And even though America’s exit from the WHO this year hasn’t made a difference in the composition of the flu vaccine, Adalja worries that the break “is likely to pose a problem when new flu strains emerge outside the United States” in the future, he says.
It is impossible to predict the course of a flu season, although vacation travel is often associated with an increase in flu infections. But experts do not rule out “a normal season in January and February”, estimates Greninger. What is clear is that flu precautions, from vaccinations to hand washing, wearing masks and staying home when sick, are more essential than ever.
Gn Health
