ATLANTA — The Centers for Disease Control and Prevention on Friday reported 12 additional human infections with influenza A (H3N2) variant virus in three states, comprising of one case in Hawaii, 10 cases in Ohio and one case in Indiana. The H3N2v virus contains the M gene from the 2009 H1N1 virus, as have the previous 17 cases detected since July 2011.
According to the U.S. Department of Agriculture, swine influenza surveillance, this swine H3N2 virus with the pandemic M gene has been detected in swine in a number of U.S. states. This virus may be circulating widely in U.S. swine at this time. It should be noted, however, that influenza viruses have not been shown to be transmissible to people through eating properly handled and prepared pork (pig meat) or other products derived from pigs.
All of this week’s reported cases occurred in people who had direct or indirect contact with swine prior to their illness. The 10 cases in Ohio were associated with attendance at a fair where reportedly ill swine were present. The H3N2v case reported by Indiana also occurred in a person who attended a fair where swine were present. The CDC continues to recommend preventive actions people can take to make their fair experience a safe and healthy one.
The number of cases of infection with H3N2v viruses with the M gene from the 2009 H1N1 virus detected in the United States since July 2011 now totals 29: Hawaii (1); Indiana (7); Iowa (3); Ohio (10); Maine (2); Pennsylvania (3); Utah (1) and West Virginia (2). According to the CDC, 23 of these cases reported swine contact prior to illness onset. Among those 29 cases, 19 cases were associated with fairs where swine were present. Most human illness with H3N2v virus infection has resulted in signs and symptoms of influenza (i.e., fever, cough, runny nose, sore throat, muscle aches) and three hospitalizations have occurred. All of the people hospitalized had high risk conditions, defined as children younger than 5 years old, seniors older than 65 years of age, pregnant women and people with chronic medical conditions (i.e., asthma, diabetes, heart disease, etc.). The CDC advised that people in these high-risk groups should avoid exposure to pigs and swine barns this summer. All H3N2v virus cases have recovered fully.
It is possible that acquisition of the M gene from the 2009 H1N1 virus may allow H3N2v viruses to be more transmissible from pigs to people and from person-to-person, the CDC cautioned. Late summer is typically fair season across the United States and fairs are a setting that can provide many opportunities for exposures to occur between pigs and people. The CDC continues to advise people to take recommended precautions when interacting with pigs or their environments, including frequent hand washing and avoiding contact with pigs that appear ill.
Studies conducted by the CDC have indicated that children younger than 10 years old would have little to no immunity against H3N2v virus, whereas adults may have some cross-protective immunity. Most cases of H3N2v have occurred in children at this time.