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Reported Infections with Variant Influenza Viruses in the United States since 2005

Please see FluView Interactive for the latest case counts.

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
Arkansas 2
Colorado 1
Delaware 1
Hawaii 1
Illinois 5 1
Indiana 154
Iowa 7 5 1
Kansas 1
Maine 2
Maryland 51
Michigan 23 1
Minnesota 9 4 6
Missouri 2
Nebraska 1
New Jersey 1
North Dakota 1
Ohio 131 3  3
Pennsylvania 17
South Dakota 1
Texas  1 1
Utah 1
West Virginia 5
Wisconsin 22 2 1
Total 434 21 13 468

For more detailed information about previously detected human cases of variant influenza infection, see Reports of Human Infections with Variant Viruses