Prevention Strategies for Seasonal and Influenza A(H3N2)v in Health Care Settings

Influenza A (H3N2) variant [(H3N2)v] virus is an influenza virus that contains genes from human, avian and swine origins. A number of human infections with H3N2v virus have been detected in the United States since August 2011 (see Case Count: Detected U.S. Human Infections with H3N2v by State since August 2011). While it is unknown whether this virus will continue to occur among humans or become more common, it is possible that health care providers will care for patients that are infected with this virus. There are no data to indicate that the transmission characteristics of the H3N2v virus will be different than those of seasonal influenza viruses. As a result, CDC advises that the infections control principles and actions relevant for seasonal influenza are appropriate for the control of H3N2v as well.

Of special note is that the current infection control guidance recommends vaccination of health care workers and patients as a critical step to reduce seasonal influenza transmission in these settings. Current CDC data indicate that seasonal vaccines may provide limited protection against infection with H3N2v viruses among adults and no protection in children. While the effectiveness of current seasonal vaccines to protect against H3N2v virus infections might be reduced compared with effectiveness of seasonal vaccines against seasonal influenza, CDC recommends their use. They remain the best tool for the prevention of seasonal influenza transmission in health care settings, which is currently the greatest risk from influenza during this influenza season.

The existing guidance can be found at Prevention Strategies for Seasonal Influenza in Health Care Settings.

CDC will update or expand this guidance as needed as more information becomes known about H3N2v.

Additional information on influenza prevention, treatment, and control can be found on Seasonal Influenza (Flu) web site.