The CDC says the infections occurred in people exposed to pigs at different agricultural fairs and are the first reported cases of swine flu in 2023.
On July 26, the Michigan Department of Health and Human Services reported a presumptive positive case of influenza A(H3)v in one person who became ill after pig exposure while attending an agricultural fair in Michigan between July 7 to 16. However, respiratory specimens sent to the CDC did not contain enough of the virus. Therefore, the CDC's diagnostic testing was inconclusive.
Still, the agency says that the person likely had the variant virus because of the presumptive positive test results and local investigations which detected swine influenza A among pigs at the agricultural fair.
The individual infected was treated with antiviral medications and recovered from the illness.
The second case involved a person who attended a different agricultural fair in Michigan between July 23 to 29. After testing respiratory specimens, the CDC confirmed the individual had influenza A(H1N2)v, a different swine flu virus variant. Again, the person was treated with antivirals and recovered.
The CDC says people in close contact with the two individuals were not infected, and no person-to-person spread has been identified.
The agency notes that viruses typically found in pigs cause sporadic infections in humans every year, primarily from exposure to pigs at agricultural fairs. When health officials identify that a swine virus caused a human infection, the virus is called a "variant flu virus," and the letter "v" is added to the viral subtype name.
While most of these infections are mild, people with a high risk of flu complications can experience severe illness from pig-related flu viruses. In addition, because of the potential for these viruses to mutate, health officials thoroughly investigate each case to ensure the swine flu virus isn't spreading among humans.
The CDC recommends that people exposed to pigs take precautions to limit the spread of these viruses between pigs and humans. These precautions include refraining from eating or drinking while in pig areas, avoiding contact with sick pigs, and washing hands with soap and running water after contact with the animals.
In addition, people at high risk of flu complications should stay away from pig barns or wear a tight-fitting mask if they cannot avoid pig exposure.