By Elizabeth Weise, USA TODAY

A cluster of flu cases linked to contact with pigs has doctors at the Centers for Disease Control and Prevention warning people to wash up and avoid eating around animals as they attend county and state fairs.

The new influenza strain sickened at least 12 people last week. All cases involved recent contact with pigs at agricultural fairs. Hawaii and Indiana each has one case, and 10 were linked to last week's Butler County Fair in Ohio. Four other cases have been linked to a county fair in Indiana that ran July 8-14. None resulted in hospitalization or death.

The new flu goes by the name influenza A (H3N2) variant, or H3N2v, and was first identified in humans a year ago, says Joseph Bresee of the CDC Influenza Division. Of the 29 cases that have been reported so far, 80% "had swine contact before getting ill and most of that contact was at county fairs," he said.

The flu is clinically identical to the regular seasonal flu, with fever, cough, sore throat and body aches. H3N2v is not a food-borne illness, Bresee says. You can't get it from eating pork. But you can get it from being around sick pigs.

To avoid H3N2v, people attending agricultural fairs and other events involving swine should take these precautions, CDC says:

• Wash hands with soap and water before and after exposure to animals.
• Avoid eating, drinking or putting anything in the mouth in animal areas.
• Don't take food or drink into animal areas.
• Pregnant women, young children, the elderly and those with chronic illnesses should avoid exposure to animal areas.
• If you develop flu symptoms after attending an agricultural fair, tell your doctor.
• Avoid sick pigs.

How do you know whether a pig is sick? Look for "a pig that's got a runny nose, goop in their eyes or they're standing away from other pigs in the enclosure," says Lisa Ferguson, a veterinarian with the Department of Agriculture's National Animal Health Policy Program.

The newly evolved virus isn't considered highly pathogenic. Of the 29 people who've had it since it was first identified, only three were hospitalized and both had underlying illnesses that made them more susceptible to the flu. Influenza is a very changeable disease, with the human form evolving yearly and requiring new vaccines. Flu in animals is much the same, with the CDC typically finding between one and seven new animal flu variants a year, Bresee says.

Scientists believe the H3N2 influenza virus, which is commonly found in pigs, managed to add a gene from the H1N1 flu virus that caused a world-wide pandemic among humans in 2009. That gene made it easier for the virus to be transmitted from pigs to people.

The good news is that although the new flu variant seems to move more easily between pigs and humans, it doesn't move easily between people.

"Because influenza viruses are always evolving, we'll watch closely to see if the virus has gained the capacity for efficient human to human transmission," Bresee says. "So far we haven't see that."

H3N2v is different enough from seasonal human flu that flu vaccine won't provide protection, he said. A possible human vaccine for H3N2v has been prepared, and clinical trails are being planned for this year.

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