Hepatitis C is a liver infection caused by a virus of the same name that is usually passed through contact with infected blood. An estimated 75 to 85 percent of infections become chronic, which can eventually cause serious diseases like cirrhosis (scarring of the liver) and liver cancer.

In one of the new studies, researchers at the Centers for Disease Control and Prevention (CDC) found that by 2007, hepatitis C was killing more Americans than HIV -- the virus that causes AIDS.

In 2007, hepatitis C killed 15,100 Americans, accounting for 0.6 percent of all deaths that year. That compared with a little over 12,700 deaths related to HIV.

Those numbers are based on death certificates, and almost certainly underestimate the real scope, according to the CDC. Compared with HIV, hepatitis C infection is more likely to still be unrecognized at the time of a person's death.

"Hepatitis C mortality has, regrettably, been on the rise for a number of years," said Dr. John Ward, director of the CDC's viral hepatitis division and an author of the new study.

But, he told Reuters Health, "many of those deaths could be prevented."

Of the estimated 3.2 million Americans with chronic hepatitis infection, about half of them don't know it, according to the CDC.

That's because the initial infection causes no symptoms in most cases. Instead, the virus silently damages the liver over the years, and people may only discover they are infected when they develop irreversible liver cirrhosis.

Chronic hepatitis C is most common in "baby boomers" -- about two thirds of U.S. infections are in people born between 1945 and 1964, Ward's team notes in their report, which is published in the Annals of Internal Medicine.

That predominance among boomers has a lot to do with casual injection-drug use back in the 1960s, 70s and 80s, since sharing tainted needles is a major route for passing on the virus.

Some people also contracted hepatitis C through blood transfusions during that era. Since 1992, all blood donations in the U.S. have been tested for hepatitis C.

Baby boomers with hepatitis C are now getting to an age where the consequences of the infection would be evident, said Dr. Harvey Alter, a researcher with the National Institutes of Health who wrote an editorial on the new studies.

"The big issue is that most people with chronic infection are still not identified," Alter told Reuters Health.

Right now, health officials recommend that certain people at increased risk have blood tests to be screened for hepatitis C. That includes anyone who's used injection drugs, people who received blood transfusions or organ transplants before 1992 and people with HIV.

"But that approach hasn't been very effective," Alter said.

Another option, Ward said, would be to screen all baby boomers.

Experts are only seriously considering that option now because of recent advances in hepatitis C treatment.

Before 1990, the infection was virtually incurable. Then researchers found that a combination of two medicines, interferon and ribavirin, could boost the cure rate to 45 percent ("cure" meaning the virus is cleared from the body).

The downside is that the regimen is hard to take. Interferon has to be injected, and the whole treatment course takes about a year. The drugs can also have side effects ranging from flu-like symptoms to sleep problems to depression.

Less than a year ago, the U.S. approved two new oral drugs that, when added to the old regimen, send the cure rate to 70 percent. Adding either one of the drugs -- boceprevir (Victrelis) or telaprevir (Incivek) -- can also cut the treatment time to about six months in some people.

The side effects are still there with the triple-drug approach. But with the high possibility of a cure, more people with chronic hepatitis C may want treatment, both Ward and Alter said.

So in a second study, the CDC researchers estimated the cost-effectiveness of doing one-time hepatitis C screening in all Americans born between 1945 and 1965.

They calculated that compared with the "status quo," screening baby boomers would catch an extra 808,580 cases of hepatitis C, at a cost of almost $2,900 for each one.

Ultimately, screening would prevent an extra 82,000 deaths, the CDC estimates -- assuming a certain percentage of people agree to treatment with interferon and ribavirin.

As far as cost-effectiveness, Ward said, that would put baby-boomer screening in line with other widely accepted types of screening, like tests for colon cancer and high blood pressure.

If screened people received one of the new hepatitis C drugs, that would save even more lives -- an additional 121,000 over current screening policy, the CDC says. But the cost would be greater, since both new drugs are very expensive.

Incivek costs nearly $50,000 for the whole course, while Victrelis rings up at roughly $26,000 to $48,000 depending on the duration of treatment.

Still, Alter, who supports baby boomer screening, said the approach looks to be "very cost-effective" -- especially when compared to the costs of treating cirrhosis and liver cancer, which are the most common reasons for liver transplants.

"The beauty of this is, it's six months to one year of treatment," Alter said.

Both Alter and Ward also pointed to other medications now in the drug industry's pipeline that are aimed at taking interferon injections out of the equation.

"Hopefully, we'll soon have oral therapies that are easier to take and have fewer adverse effects," Alter said.

For now, the screening focus in the U.S. is on baby boomers. Whether it could be a good idea in younger generations is not clear.

New hepatitis C infections in the U.S. are down sharply since the 1980s, according to a CDC study published last year.

In the mid-1980s, roughly 70 of every million Americans developed acute hepatitis C each year. Between 1994 and 2006, that rate was 90 percent lower: only seven per million per year.

As it stands, there are roughly 18,000 new hepatitis C infections each year -- most of which occur in injection-drug users.

SOURCE: bit.ly/xOLGYg and bit.ly/xzj1ve Annals of Internal Medicine, February 21, 2012.

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