ATLANTA (AP) -- Don't pet the pigs.

That's the message state and county fair visitors got Thursday from health officials who reported a five-fold increase of cases of a new strain of swine flu that spreads from pigs to people. Most of the cases are linked to the fairs, where visitors are in close contact with infected pigs.

This flu has mild symptoms and it's not really spreading from person to person.

"This is not a pandemic situation," said Dr. Joseph Bresee of the Centers for Disease Control and Prevention.

But any flu can be a risk for some people, and people should be cautious when they can, he added.

The case count jumped from 29 a week ago to 158 this week, thanks to a wave of new cases in Indiana and Ohio, said Bresee, the agency's chief of influenza epidemiology.

Most of the infected patients are children -- probably because many were working closely with raising, displaying and visiting pigs at the agricultural fairs, Bresee said.

The recent cases include at least 113 in Indiana, 30 in Ohio, one in Hawaii and one in Illinois, Bresee said in a conference call with reporters.

The count is changing rapidly. Indiana health officials on Thursday afternoon said they had seven more confirmed cases than Bresee noted. That would raise the grand total to 165 so far.

Also, diagnosis of cases has become quicker in the last week. CDC no longer must confirm a case with its own lab. Now states are using CDC test kits to confirm cases on their own on, speeding the process along. The newly reported cases were likely infected a week or two ago.

The CDC has been tracking cases since last summer. A concern: The new strain has a gene from the 2009 pandemic strain that might let it spread more easily than pig viruses normally do.

The good news is the flu does not seem to be unusually dangerous. Almost all the illnesses have been mild and no one has died. Two of the recent cases were hospitalized, but both recovered and were discharged, Bresee said.

More good news is that all of the recent cases appear to have spread from pigs to humans, meaning it's not very contagious, at least between people. But there probably will be more cases in the weeks ahead, and it won't be surprising if at least a few of them involve person-to-person transmission, Bresee said.

Pigs spread flu virus just like people do, with coughing, sneezing and runny noses, so people can get it by touching pigs or being near them.

Health officials don't think it's necessary to cancel swine shows, but are urging people to take precautions.

Fairgoers should wash their hands and avoid taking food and drinks into livestock barns, officials said, while pregnant women, young children, the elderly and people with weakened immune systems should be particularly careful.

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