Reported Infections with Variant Influenza Viruses in the United States since 2005
When people are infected with influenza A viruses that are known to be genetically similar to viruses circulating in swine, these viruses are called “variant viruses” and denoted with a letter “v”. The table below reflects the most current case counts for variant virus infections reported in the United States since 2005.
Most infections with variant viruses have occurred in children (persons 18 or younger) and most cases have reported direct or indirect exposure to swine prior to onset of illness. Limited transmission from close contact with an infected person has been observed in some investigations of human infections with variant viruses, but sustained human-to-human transmission has not been documented.
Table. Case Count: Detected U.S. Infections with
Variant Influenza Viruses by State since December 2005
|Reporting State||H3N2v||H1N1v||H1N2v||Total Detected Influenza
Variant Virus infections
For more detailed information about previously detected human cases of variant influenza infection, see Reports of Human Infections with Variant Viruses
† On August 18, 2017 a variant case in Pennsylvania was reported in FluView. As of this time, that case has been characterized as an influenza A (H3) variant (H3v) virus. Further analysis is being performed at CDC to characterize the neuraminidase protein of this virus.
- Page last reviewed: August 11, 2017
- Page last updated: August 18, 2017
- Content source:
- Centers for Disease Control and Prevention, National Center for Immunization and Respiratory Diseases (NCIRD)
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