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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.

H3N2v

Beginning in August 2011, infection with an H3N2v virus was detected in a number of people across several U.S. states. More information about H3N2v is available at Influenza A (H3N2) Variant Virus Outbreaks.

Table. Case Count: Detected U.S. Infections with
Variant Influenza Viruses by State since December 2005

Reporting StateH3N2vH1N1vH1N2vTotal Detected Influenza Variant Virus infections

Arkansas

 

2

  

Hawaii

1

  

Illinois

5

1

 

Indiana

154

  

Iowa

6

3

 

Kansas

1

  

Maine

2

  

Maryland

12

  

Michigan

8

 

1

Minnesota

8

2

4

Missouri

 

2

 

Ohio

110

2

 

Pennsylvania

16

  

South Dakota

 

1

 

Texas

 

1

 

Utah

1

  

West Virginia

5

  

Wisconsin

21

2

 

Total

350

16

5

371

* Includes H3N2v viruses with the M gene from the influenza A (H1N1)pdm09 virus and without the M gene from the influenza A (H1N1)pdm09 virus.

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

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