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When it comes to hepatitis C, things that happened to baby boomers back in the day can make all the difference.

One in 30 baby boomers is infected with virus, says the Centers for Disease Control and Prevention. And most of them don't know it. So, the CDC is moving ahead with a proposal that all baby boomers (born between 1945 and 1965) get a blood test to check for the virus.

The current guidelines call for testing when someone has known risk factors.

Such as? Blood transfusions or organ transplants before 1992 (when effective screening for hepatitis C virus became common), or recreational injection of drugs — even once — could have led to a liver infection that has gone undetected all these years.

But just being a baby boomer is risk factor enough, the CDC has concluded. "Baby boomers are five times more likely than other American adults to be infected with the disease," the CDC says. "In fact, more than 75 percent of American adults with hepatitis C are baby boomers." Infection rates were highest in the '70s and '80s.

All told, the CDC figures that one-time testing of the group could uncover 800,000 more cases of infection. About 3.2 million people Americans are thought to be infected with the liver-damaging virus.

Hepatitis C symptoms can be mild or nonexistent, so it's not unusual for someone who's got the virus to be unaware of it.

Over time, though, hepatitis C can damage the liver. The virus is the leading cause of liver cancer and liver transplants. And a recent analysis by the CDC found that more people in the U.S. die from hepatitis C than HIV/AIDS.

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