Flu admissions jump 91% in 1 week; New York sees record cases — 5 updates

A mutated version of an influenza A strain is dominating this year’s respiratory virus season, driving a record number of cases in some areas of the country. More than half of states reported “high” or “very high” levels of flu-like illness for the week ending Dec. 20, according to the CDC’s latest FluView report. 

Public health experts anticipate continued increases over the next few weeks, noting that current data does not yet capture infections tied to holiday travel and gatherings.

Five flu season updates:

1. At least 19,000 patients with laboratory-confirmed flu were hospitalized in the week ending Dec. 20, marking a 91% increase from the week prior, according to CDC data. The weekly hospitalization rate also increased week over week from 3.1 to 5.6 per 100,000 population.

Current forecasts from the agency indicate this virus season will result in a similar level of flu admissions as last season, which was the most severe since 2010. Between 610,000 and 1.3 million people were hospitalized for the flu during the 2024-25 season, according to CDC estimates.  

The CDC estimates there have been at least 7.5 million flu cases, 81,000 hospitalizations and 3,100 deaths so far this season, including eight pediatric flu deaths.

2. Twenty-nine states reported “high” or “very high” levels of flu-like illness for the week ending Dec. 20, in addition to New York City and the District of Columbia, which HHS reports as individual jurisdictions. More than 6% of outpatient visits were due to respiratory illness that week, above the national baseline of 3.1%.

3. ED visits for the flu have also been rising steadily over the past several weeks. Flu accounted for 5.4% of ED visits for the week ending Dec. 20, up from 2.9% the week prior. Children are especially affected, with flu responsible for 12.3% of ED visits among children and infants up to age 4, and 17% among those ages 5 to 17.

4. In New York state, more than 71,000 cases were reported for the week ending Dec. 20 — the highest weekly total recorded since the state began tracking cases in 2004, health officials said in a Dec. 26 briefing, according toCBS News. 

Earlier this month, leaders at New Hyde Park, N.Y.-based Northwell Health said a rise in respiratory viruses, particularly flu, was already straining its emergency departments, urgent care and primary care practices.

Nearly 10,000 patients visited EDs in New York City with flu-like symptoms for the week ending Dec. 20. This marks the highest weekly total in the past decade and coincides with the record case total.

5. Experts believe a mutated version of H3N2, which is a subtype of influenza A, is behind the current surge in cases. The strain, known as “subclade K,” acquired several new mutations over the summer that help it better evade existing immunity and spread more efficiently. While not linked to more severe illness, the strain is not a close match to this year’s vaccine. Still, experts stress that vaccination remains a key tool for reducing the risk of severe disease, particularly among high-risk populations.

CDC data shows H3N2 viruses are the most frequently reported types of influenza viruses so far this season. 

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