The Centers for Disease Control is warning people to be careful around pigs because of a new flu found in them that can spread to people.

The agency is highlighting state and county fairs, which are common at this time of year and often feature pigs.

Officials say 29 human cases of the new strain of swine flu have been confirmed in the U.S. in the last year, most of them children.

Ten of the 12 cases confirmed this week were linked to the Butler County Fair in southwest Ohio, which ended last weekend.

The Centers for Disease Control and Prevention has been tracking sporadic Swine Flu cases since last year, when the new strain was first seen in people. The concern is the new strain has a gene from the 2009 pandemic strain that might let it spread more easily than pig viruses normally do.

So far, that seems to be the case for pigs to people, but it hasn't been spreading easily from person to person — which is the greater concern.

It also has not been unusually dangerous. All of the recent cases were mild, as were most of the earlier illnesses.

But even regular flu can be a serious illness, so people should be careful if they're going be around pigs, said Dr. Joseph Bresee, the CDC's chief of influenza epidemiology.

Fairgoers are advised to wash their hands and avoid taking food and drinks into livestock barns. Pregnant women, young children, the elderly and people with weakened immune systems should be particularly careful.

With summer and fall fairs, "we're likely to see additional cases," Bresee told reporters during a teleconference Friday. He said work has begun on a vaccine for the new strain in case it ever becomes more of a threat.

Meanwhile, officials at state fairs in Ohio and Indiana say they'll be watching for any signs of swine flu. The Ohio State Fair sent home two pigs with the flu this week.

This is based on a story by The Associated Press.

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