Two more children in Pennsylvania were infected with a novel swine influenza A/H3N2 virus that includes a gene from the 2009 pandemic H1N1 virus, raising the number of such infections in the state to three, the Pennsylvania Department of Health (PDH) announced yesterday.

The two children, like the first case-patient reported Sep 2, attended the Washington County Agricultural Fair in southwestern Pennsylvania the week of Aug 13 to 20, PDH officials said in a press release. The first patient has recovered, and the other two patients are recovering, they said.

On Sep 2 the Centers for Disease Control and Prevention (CDC) announced that one child each in Indiana and Pennsylvania had been infected with a swine-origin H3N2 virus that included the matrix gene from the 2009 H1N1 virus. The viruses were described as similar but not identical. Both of the children recovered. The Indiana child might have caught the virus from a caregiver who had had contact with pigs, the CDC said.

Investigators from the PDH and CDC have not yet determined exactly how the three Pennsylvania patients became infected, according to the PDH. The earlier CDC announcement, however, said the first patient, a girl, was exposed to pigs and other animals at the fair.

None of the three patients had any direct link to the others, according to Brandi Hunter-Davenport, a PDH spokeswoman. "Their only commonality was attending the fair," she told CIDRAP News today.

She said the latest patients have had typical flu-like symptoms. Citing confidentiality concerns, she declined to give their ages.

Hunter-Davenport also said no information was available yet on whether pigs at the fair were infected with the novel virus. "We´re still investigating what the linkages are here, if it´s human-to-human or animal-to-human transmission," she said.

The PDH and CDC are increasing surveillance in southwestern Pennsylvania and setting up information booths at agriculture fairs, and the Pennsylvania Department of Agriculture is monitoring the health of animals at fairs, according to the PDH release.

The statement said anyone who attended the Washington County Fair and has flu-like symptoms should contact their local health provider or call the health department.

State officials also said people should take everyday precautions to prevent the spread of respiratory viruses and should wash their hands after having contact with animals at fairs and other public places.

"We´re not telling people to avoid public venues or fairs," said PDH Secretary Dr. Eli Avila, in the press release. "But, until we complete our investigation, we want to make sure that the public is aware and is taking the proper precautions to protect their health."

In its Sep 2 announcement about the first two cases, the CDC said the viruses are similar to eight other swine-origin H3N2 viruses found in humans in the past 2 years, but different in that they contain a gene from the 2009 H1N1 virus. The agency said reports of human infections with swine-origin flu viruses have increased in recent years, at least partly because of increased testing and recent reporting recommendations.