Seasonal Flu Update: Dec 2025

Flu season in New York State has started with a bang. In addition to the expected A and B strains, there has been a late emergence of an additional flu strain mutation (influenza A H3N2 mutated from a “J” subclade to a “K” subclade). Subclade K has quickly become the dominant strain in the U.S. and a number of other countries. It is not unusual for there to be mutations such as this, but because the flu vaccine must be produced many months in advance, the unexpected emergence of a new or mutated strain can result in a mismatch between the seasonal flu vaccine and the currently circulating flu strains. While this means the vaccine’s effectiveness may be lower, it can still decrease the incidence of severe disease, hospitalization and death. 

Typically influenza A strains are more dominant early in the flu season and influenza B strains are more dominant later in flu season. The peak of flu season in New York state is usually January-February.  

Infections and Hospitalizations on the Rise 

At this time the majority of hospitalized cases for respiratory illness throughout the state are flu-related. Both reported flu cases and flu hospitalizations have risen dramatically over the past 2 weeks, according to the NYS Department of Health. Flu rates by county can be found on the Department of Health website. 

Infection Control in Healthcare Settings–Flu is Airborne! 

Although the CDC had been moving towards the World Health Organization’s definition of airborne transmission as not being via either droplet or airborne particulate, but rather both simultaneously, they have quietly moved back to the old, disproven theory that flu is spread mostly through contact and that large droplets that do not spread far from the patient. “Droplet controls” usually only include wearing a surgical or procedure mask when in close contact with the infected patient. However, numerous scientific studies have proven that influenza and other respiratory diseases are also spread via smaller, lighter airborne viral particulates that travel farther and stay in the air longer than relatively big, heavy droplets. That means a fit-tested respirator, such as an N95, PAPR or CAPR, must be worn to prevent inhaling these pathogens, and ventilation must be improved to keep the airborne viral load as low as possible. 

Ventilation can also be improved by:

• Placing infectious patients in airborne infection isolation rooms (negative pressure rooms).
• Running portable HEPA filters in patient rooms.
• Installing ventilated headboards or hoods.
• Increasing the amount of fresh air that moves through rooms. 

More information on infection controls can be found on the NYSNA website. 

Vax or Mask 

As a reminder, the New York State Health Commissioner declared influenza prevalent in New York state as of December 2, 2025. That means that all personnel working in healthcare facilities throughout the state must be vaccinated against seasonal influenza or wear a surgical or procedure mask in areas where patients or residents are typically present (per Section 2.59 of the New York State Sanitary Code, 10 NYCRR § 2.59). More information on the New York state requirement for masking of non-vaccinated healthcare personnel can be found on the Department of Health website.  

Need Help? 

If you have any questions or concerns regarding flu activity and infection control in your facility, please contact the NYSNA Occupational Health and Safety Representatives at healthandsafety@nysna.org.