Hepatitis C rate may be down in the U.S.: study

A new study finds that the percentage of U.S. blood donors with evidence of hepatitis C infection is substantially lower now than in the early 1990s - in what researchers say probably reflects an overall decline in the infection rate among Americans.

The findings also hint at a link between multiple pregnancies and the virus, and of a protective effect of obesity, although it's too soon to tell whether these associations will hold up.

Hepatitis C is a viral infection passed through contact with infected blood - most often by sharing tainted needles - though a small number of cases are sexually transmitted or passed from mother to baby during childbirth.

In a minority of people, the body is able to clear the virus soon after infection. However, the infection becomes chronic 75 percent to 85 percent of the time, often leading to liver damage such as chronic inflammation, scarring of the liver tissue (cirrhosis) and, in some cases, liver cancer. The U.S. Centers for Disease Control and Prevention estimate that between 1 and 5 percent of people infected with hepatitis C eventually die of cirrhosis or liver cancer.

Since 1992, the U.S. donor-blood supply has been screened for hepatitis C, and the risk of receiving a donation carrying the virus is now estimated at one in 2 million, according to the National Heart, Lung, and Blood Institute.

Based on studies from the early 1990s, about a half a percent of U.S. blood donors between 1992 and 1993 harbored antibodies to hepatitis C - which indicates either a chronic infection or a past infection that cleared.

The rate in more recent years had been unclear, however.

In the new study, published in the Journal of Infectious Diseases, researchers analyzed samples from nearly 960,000 donors who gave blood at six U.S. blood banks between 2006 and 2007.

They found that less than a tenth of a percent of donors tested positive for antibodies to hepatitis C.

"It's a strikingly lower prevalence" compared with 1992-1993, said lead researcher Dr. Edward L. Murphy, of the University of California, San Francisco.

The decrease, Murphy told Reuters Health, likely reflects, in part, an overall decline of hepatitis C infection among relatively younger Americans. The "Baby Boomers" born between the late 1940s and early 1960s had higher rates of injection-drug use than subsequent generations, and therefore a higher risk of carrying hepatitis C.

In support of such a "birth cohort effect," Murphy's team found that in 2006-2007, donors in their 40s and 50s had the highest rate of hepatitis C compared with other age groups. In the early 1990s, the highest rates had been seen among donors in their 30s and 40s.

The findings, according to Murphy, suggest that the Baby Boomer generation is likely to have the highest rate of hepatitis-C- related liver disease, and that the rate will decline among younger Americans.