(Updated Aug 11: CDC has raised the number of people confirmed infected to 153)

As many as 153 people have been infected this summer with a new pig flu virus, the U.S. Centers for Disease Control and Prevention said this week, although the disease does not appear to be any more serious than normal seasonal flu. Nine out of 10 of them are children, CDC says.

Most cases appear to be among people who were showing pigs, or people visiting fairs and other places where these pigs are, CDC says. This suggests they are catching the flu directly from infected pigs. So far everyone has gotten better on their own, Dr. Joseph Bresee, from the CDC's influenza division, told reporters on a telephone briefing Thursday.

“At this point there is no evidence of sustained, efficient human to human spread,” Bresee said. “This is not a pandemic situation.”

But Bresee cautioned that even seasonal flu can kill people and this is likely the case with the new form of flu, which is designated H3N2v.

The new strain of H3N2 was first seen last year, and three people were confirmed to have caught the bug from other people. So far it has not been any more serious than regular, seasonal flu, causing fever, a sore throat and achy muscles. Last year no one ended up in the hospital with the new flu. This year, two people have but they are fine now, Bresee said.

While the current flu vaccine does not protect against this new virus coming straight from pigs to people, patients can be treated with the two drugs that work against seasonal flu – Tamiflu and Relenza.

Most of the cases have been in Indiana, where 120 have been reported, the CDC said. There have also been 31 cases in Ohio, one case in Hawaii and one case in Illinois.

Flu viruses have eight genes, and this one is seven-eighths pig virus -- a virus designated H3N2 that’s been circulating among swine for years. But one single gene comes from the H1N1 swine flu virus that caused a new pandemic of influenza  among people in 2009 and which is now part of the human seasonal flu mix.

The names can be confusing because there's also an H3N2 virus that causes seasonal flu in people, and it's one of the three strains of flu virus that is included in the vaccine that's just arriving in doctor's offices and clinics now. "Get your flu vaccine," Bresee advised. "Everybody should get a flu vaccine this year in the U.S. because regular, seasonal flu will be here soon."

CDC stressed that only people who have contact with pigs are at any real risk of catching this flu. "This time of year is the time when you have state and county fairs…there’s thousands of them," Bresee said. CDC has some simple advice to prevent infection:

• Wash your hands after you've been near any live pigs
• Don't bring any food or drink into areas where live pigs are
• Stay away from swine if you are at high risk from flu, for instance if you are elderly or have a weakened immune system.

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