The flu is surging across the United States during the busy holiday travel season, with New York among the hardest-hit states.

For the week ending December 20, New York had its highest number of flu infections ever recorded in a single week, 71,123, according to the New York State Department of Health.

'This is a rise of 38 percent over the previous week. There have been 189,312 positive flu cases reported in New York this season to date,' the state health department added.

As of December 13, New York — along with New Jersey, Louisiana, Colorado and Rhode Island — has reported 'very high' numbers of outpatient visits to medical providers complaining of flu-like symptoms, according to the Centers for Disease Control and Prevention.

Another 10 states have 'high' numbers of flu-related checkups this year. They include Massachusetts, Connecticut, North Carolina, South Carolina, Maryland, New Mexico, Idaho and Michigan.

Cases are also elevated in Washington, D.C. and Puerto Rico, an unincorporated US territory.

The CDC has also concluded that infections are on the rise in 47 states, a prediction current as of December 16. The only state where cases are declining is Hawaii.

'Seasonal influenza activity continues to increase across the country. The timing of this increasing activity is similar to several past seasons,' the CDC said in a bulletin on December 19.

Flu infections are on the rise in 47 states, according to the Centers for Disease Control. The only state where infections are on the decline is Hawaii

Rising flu cases are coinciding with one of the busiest times to travel of the year 

What could complicate things is that there is a new flu variant, subclade K, a variant of the influenza A(H3N2) virus.

This particular virus wreaked havoc on the populations of Japan, the UK and Canada.

Doctors and other health officials are worried that the current flu vaccine won't fully protect against the mutated virus. However, they're convinced that getting a vaccine will still provide you with more protection than not.

'So, whether we're simply seeing more cases because this clade K influenza virus is evading immunity, and therefore more people are susceptible to infection, or if it's really causing more severe disease on a case-by-case basis is still something that is not completely clear,' said Andrew Pekosz, who is the co-director of the Johns Hopkins Center of Excellence in influenza research and response.

'But what is clear is that cases are increasing, and we're seeing a lot of influenza. Cases are increasing across the country, and that's a trend that we're sure will continue into the new year,' Pekosz said.

Americans are also getting fewer flu shots than they did last year. More than 47.6 million vaccinations were administered at pharmacies and doctors' offices during the 2025/2026 season.

That is about three million fewer than last season's tally. 

Jennifer Nuzzo, professor of epidemiology and director of the Pandemic Center at Brown University School of Public Health, said the government shutdown throughout October and into almost half of November led to a lack of data collection during that period. 

Nuzzo's comments were made in a flu report published in the Journal of the American Medical Association on December 19.

'We’re potentially heading into a flu season that could be quite a doozy, and we know we’re starting it with fewer data and, more crucially, fewer vaccinations,' she said.

H3N2 has a series of symptoms to watch out for, including fever, cough, runny nose, and fatigue. Muscle aches and chills are also common side effects

The CDC has estimated that at least 4,600,000 illnesses, 49,000 hospitalizations, and 1,900 deaths from flu have occurred so far this season. So far, three children have died.

H3N2 has a series of symptoms to watch out for, including fever, cough, runny nose, and fatigue. Muscle aches and chills are also common side effects.

Leading medical organizations around the world say it isn't too late to get a flu shot, with everyone six months or older being eligible, save for anyone with allergic reactions to ingredients in the vaccine or previous negative reactions.

To prevent the spread of the flu, like most viruses, it's essential to wash your hands thoroughly (for at least 20 seconds) with soap and water.

It's also important to avoid touching your eyes, nose, and mouth with unwashed hands. Health authorities have also advised people to stay home if they're sick and to avoid contact with others who are ill.

Finally, it's recommended to cover coughs and to disinfect frequently touched surfaces like counters and doorknobs.