As signs point to a more-severe-than-normal flu season this year, hospitals might see more congestion among patients and in physical capacity.
Several variables are intensifying this outlook as a new variant emerges, inoculation rates fall and measles outbreaks grow.
1. A new variant
Overall flu activity is low, with influenza-related cases accounting for less than 1% of emergency department visits. A whisper of a more severe season is growing into a roar, though. Clinical laboratories have detected a majority of influenza A specimens, which usually cause more severe illness, particularly in young children and older adults.
A version of the H3N2 subtype, which is a type of influenza A, is spurring earlier and more intense flu outbreaks in Canada, the United Kingdom and Japan. Half of H3N2 cases are coming from a new variant called subclade K.
UK Health Security Agency scientists told CNN subclade K is expected to dominate this season, and approved flu vaccines cover an adjacent group of viruses, meaning vaccine efficacy might be lessened from past years.
In the U.S., flu-related ED visits are rising among children, according to the CDC’s FluView report, which reflects national data as of Nov. 8. The latest week also saw increases in percent positivity for influenza across pediatric age groups, the CDC said.
2. Declining vaccination rates
As people travel and gather for winter holidays, fewer of them are receiving vaccinations against flu and numerous other viral infections.
Last year, less than half of U.S. adults and children received a flu vaccine, according to the CDC. For the 2025-26 influenza season, flu shot producer CSL predicts vaccination rates to fall 12% overall, including a 14% decline among adults 65 and older.
So far, flu vaccination rates are down 8% compared to last year. Between August and the end of October, retail pharmacies administered about 26.5 million flu shots — roughly 2 million fewer than the 28.7 million administered during those months in 2024, according to prescription data IQVIA provided to CNN.
3. Ongoing measles outbreaks
In 2000, the U.S. achieved measles elimination status. Twenty-five years later, the nation risks losing it.
During a Nov. 17 call with state health departments, CDC officials tied a measles outbreak originating in West Texas to another in Utah and Arizona, according to The New York Times. Countries with sustained transmission of measles for over a year lose their “elimination status” as determined by the World Health Organization. Last week, Canada lost its 27-year streak as a country that had eliminated measles.
The West Texas measles outbreak began in January 2025 and ended in August. Its association with the outbreak in Utah and Arizona, however, means the U.S. has only a few weeks to quash the largest measles outbreak currently in the country, according to the Times.
As of Nov. 12, the CDC has confirmed 1,723 measles cases across 43 states. The outbreak has worsened throughout 2025, and with early pressures appearing in the 2024-25 flu season, hospital capacity might further strain.
