The Centers for Disease Control in Atlanta raised the number of recorded cases of influenza A (H3N2) variant virus infections to 29 from 17.
An additional 12 cases of H3N2v were reported in Hawaii (1 case), Ohio (10) and Indiana (1).
CDC said all the reported cases occurred in people in direct or indirect contact with swine before their illness.
Ten cases in Ohio were associated with a fair where sick pigs were present, CDC said.
The case reported in Indiana also occurred in a person who attended a fair.
Among the 29 cases, 19 were associated with fairs where swine were present.
Three people have been hospitalized so far because those persons had high-risk conditions, CDC said.
Symptoms and signs of H3N2v virus infection include fever, cough, runny nose, sore throat and muscle aches.
The US Department of Agriculture said swine influenza surveillance has detected the virus with pandemic M gene in swine in a number of states.
The virus may now be circulating widely in US swine, however, the virus has not been shown to be transmissible through eating properly handled pork or pork-based products, CDC said.
CDC is advising the general public to exercise precautions when attending fairs because there are more opportunities for interactions between pigs and people.
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