H3N2 outbreak sickens hundreds

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More than 300 people had reported illnesses as of late September in an influenza outbreak connected with contact with pigs at fairs.
Since July 2012, a 61-year-old woman has died and 16 people have been hospitalized with infections with the influenza A H3N2 virus variant, according to the Centers for Disease Control and Prevention and the Ohio Department of Health. The 61-year-old had close contact with pigs at an Ohio fair prior to her death in August 2012, and information from the CDC and Ohio authorities indicates she also had chronic illness from multiple medical conditions.
About 80 percent of the outbreak’s illnesses have occurred in Indiana and Ohio. Except for a case reported in Hawaii, the rest of the infections have been reported in the Midwest and East. The infection in Hawaii is believed to be connected with a small herd of pigs at the person’s home, although those interviewed in connection with the illness indicated they did not notice any ill pigs.
By Aug. 9, the CDC reported that all people reached in response to the outbreak investigations indicated they had contact with swine or attended a fair where swine were present. Michael A. Jhung, MD, a medical officer with the CDC’s influenza division, said in mid-September that a few of the illnesses in the outbreak are believed to have resulted from human-to-human transmission, but the CDC has not seen any evidence of efficient or sustained transmission among people.
Agency officials also have reported that the outbreak H3N2 strain contains an M gene shared with the 2009 pandemic H1N1 influenza virus. Dr. Jhung said the M gene’s significance is uncertain, but some studies with animal models have indicated it could help transmit the virus between pigs and people. He said those at the CDC don’t think the gene alone is responsible, but it may contribute to transmissibility.
Officials with the Department of Agriculture’s swine influenza virus surveillance program have identified the M gene in about 60 of 140 pigs found to be infected with H3N2 viruses between Oct. 1, 2011, and July 31, 2012. Department information states that the surveillance is intended to identify types of viruses circulating among swine and not to define prevalence.
The CDC is warning people who exhibit pigs to watch the animals for illness, contact veterinarians if they suspect illness, and take protective measures such as avoiding contact with pigs that appear to be ill and wearing protective equipment when contact is needed.