Where the flu currently stands

According to data from Epic Research, flu rates have had their earliest start since the COVID-19 pandemic. For the week of Sept. 13, flu encounters reached 140.6 per 100,000 people, which is the highest level of flu in mid-September in five years and double the rate of the same week in 2024 and 2025.

Hospitals are also reporting more flu cases than usual. For example, Seattle Children's recently reported 150 pediatric flu cases in two weeks, a significant increase from the 10 cases seen during the same period last year. Typically, the health system does not see that level of flu cases until early December.

"We're about two months early," said Danielle Zerr, head of pediatric diseases at Seattle Children's.

According to CDC, 49 states and the District of Columbia are all reporting minimal influenza-like illness (ILI) levels, while Louisiana is reporting low ILI levels. Although national flu activity is still low, it has been increasing across the country since late August and early September, with the highest activity occurring on the West Coast.

For the week ending Oct. 3, the flu test positivity rate was 3.6%, an increase from the week before. In addition, CDC noted that 1.8% of patient visits reported to the agency were due to an ILI, a rate that is below the national baseline of 3.1% and remained stable compared to the previous week.

CDC also noted that while the weekly hospitalization rate for influenza observed during the week ending Oct. 3 was just 0.6 per 100,000, that rate has been increasing since August. A total of 3,334 people were admitted to the hospital with the flu during the week ending Oct. 3, with the most hospitalizations occurring among those ages 65 and older.  

Why this year's flu season is starting early

Thomas Russo, a professor and chief of infectious disease at the University of Buffalo, said he's "surprised" this year's flu season is starting early.

"We had a couple of back-to-back flu seasons, and people developed immunity that should still offer some protection — but this is happening at least four weeks earlier than usual," he said.

Caitlin Rivers, an epidemiologist at the Johns Hopkins Bloomberg School of Public Health, agreed. "It's very uncommon to see flu activity rising this early," she said. "It's activity that we might normally see more like November or December."

What's also strange is the fact that flu activity seems to have started in Western states like California, Washington, Hawaii, and Alaska.

"It typically starts in the South and then expands from there," Rivers said. "So two uncommon developments there."

However, Rivers stressed that the amount of flu activity is still very low in the majority of the country, though that's starting to change as the disease picks up nationwide.

While it would be easy to blame low vaccination rates, experts said that's unlikely to cause a rise in cases at this point in the year. "Many people are not vaccinated yet at this time every year," said Russo.

Adalja agreed. "That's the normal baseline, not a new factor," he said. "Low vaccination rates matter for how severe a season gets, but they don't explain why it started early."

Adalja also noted that just because the flu season is starting early doesn't mean it will necessarily end early. "Seasons often come in waves, driven by different strains, so an early H1N1 surge can be followed by H3N2 or influenza B later," he said. "An early start tells you little about when the season will end or how bad it will be."

With the flu season starting early, experts are urging people get their flu shot as soon as possible. "It's crucial that people get an influenza vaccine," said Scott Hensley, a virologist at the University of Pennsylvania. "And this might be a year that people might want to get a vaccine early."

Peter Chin-Hong, an infectious disease expert at the University of California, San Francisco, said that people should aim to get their flu shot ideally before mid-October. The current variant appears to be similar to last year's strain and is included in this year's vaccine, which should reduce concern about a mismatch between the vaccine and the flu, he said.

"The ball is in our court because vaccination behavior drives how we tackle the flu," Chin-Hong said. "This year we have less excuse because the flu vaccine is well-matched in general to ... what has been circulating so far."