Where the 2025-26 flu season stands

Flu activity around the United States has declined significantly compared to its peak in the winter. CDC data shows that for the week ending Mar. 28, all but nine states are experiencing "low" or "minimal" influenza-like illness (ILI) activity.

Meanwhile, eight states are experiencing "moderate" ILI activity, including:

• Colorado
• Idaho
• Massachusetts
• New Hampshire
• New Jersey
• New York
• Ohio
• Oregon

New Mexico is currently the only state experiencing "high" levels of ILI activity, according to CDC.

For the week ending Mar. 28, CDC found that 9.8% of clinical lab tests were positive for influenza and 2.6% of visits to a healthcare provider were for respiratory illness, both of which are lower than the week prior. In addition, there were four influenza-associated pediatric deaths for the week ending in Mar. 28, bringing the total number of influenza-associated pediatric deaths for the 2025-26 flu season to 127.

Since Oct. 1, 2025, CDC estimates there have been at least 30 million flu illnesses, 14 million flu medical visits, 370,000 flu hospitalizations, and 23,000 flu deaths.

While flu rates are declining as the season comes to an end, CDC said in a recent update that cases of respiratory syncytial virus (RSV) are elevated later than expected, noting that RSV cases increased later than usual throughout most of the United States.

"This unusual timing means higher levels of RSV activity may continue into April in many regions," CDC said. "Emergency department visits and hospitalizations for RSV are highest among infants and children less than 4 years old."

For this year's vaccine, CDC found it was around 25% to 30% effective in preventing outpatient visits or hospitalization from the flu in adults and around 40% effective in preventing outpatient visits or hospitalization from the flu in children.

Typically, health officials are pleased if a flu vaccine is between 40% and 60% effective, though past CDC research suggests this season saw one of the lowest effectiveness rates in the past 20 years.

Flu infections in the U.S. surged in late December and were especially intense in some areas of the country, with New York City health officials calling it the most intense season in 20 years.

While somewhat low flu vaccination rates didn't help, experts blamed the new strain of influenza that was causing most infections for the low effectiveness rate. The new strain belonged to a category of flu virus called A H3N2 and was called subclade K. This version of the virus seemed to spread more easily, though it didn't cause more severe illness.

The flu vaccine available for this season was built to address a different version of H3N2 and the new strain's prevalence is likely why the vaccine was less effective, according to William Schaffner, a vaccine expert at Vanderbilt University.

Work is already underway on the flu vaccine for next season. In February, the World Health Organization (WHO) announced its recommendations for which strain the flu vaccine should address for the 2026-27 northern hemisphere season, saying vaccines should be built to handle subclade K. Last month, an FDA advisory committee endorsed WHO's recommendations.