Epidemiology

U.S. hepatitis C cases down sharply since 1980s

Last Updated: 2011-02-15 19:45:24 -0400 (Reuters Health)

By Amy Norton

NEW YORK (Reuters Health) - Acute hepatitis C is far less common these days in the U.S. compared to the early 1980s, a new government study finds.

According to the new study by researchers at the U.S. Centers for Disease Control and Prevention (CDC), in the mid-1980s roughly 70 of every million Americans developed acute hepatitis C each year. Between 1994 and 2006, that rate was 90% lower: only 7 per million per year.

Over the years, however, injection drug users have accounted for a growing proportion of cases, and their risk of infection remains an important public health problem, the CDC researchers said in a February 14th online paper in the Archives of Internal Medicine.

So far, efforts to curb hepatitis C transmission among drug users "have had success to some degree," said Dr. John Ward, director of the CDC's division of viral hepatitis, in an interview. Ward didn't work on the new study, which was led by Dr. Ian T. Williams.

Dr. Williams and colleagues looked at rates of acute hepatitis C reported in six U.S. counties between 1982 and 2006. They note that tracking rates of acute hepatitis C as they rise or fall gives researchers an idea of whether rates of silent new infections are rising or falling, too. About 20% to 30% of new infections are symptomatic, they said.

In addition to finding that the rate of new infections had dropped, they made some discoveries about certain high-risk groups.

Among people receiving transfusions, for example, the risk of infection from hepatitis C virus in the blood has steadily declined over time, with only five possible cases identified between 1994 and 2006.

The number of cases reportedly related to injection drug use also declined over time. But drug abuse accounted for a growing proportion of acute hepatitis C infections, rising from about 32% of cases in the 1980s to at least 46% for the years 1994 through 2006.

In another third of cases, there was no clear risk factor, but most of those people reported past drug abuse.

Efforts to curb HIV transmission among injection drug users -- through education and needle-exchange programs, for example -- have been very effective, according to Dr. Ward.

But it's been harder to battle hepatitis C.

The knowledge of what to do to prevent hepatitis C among injection drug users "is just not as deep as it is for HIV," Dr. Ward said.

The other ongoing public health concern with hepatitis C is the large number of Americans with chronic infection who may develop serious liver disease in the future. It's estimated that 3.2 million Americans are living with chronic hepatitis C, Dr. Ward said, and about half are unaware of it.

Regarding the lower rates of new infections, he told Reuters Health, "That's great news."

"It shows that prevention can work," he added. "But our work is not done."

SOURCE: http://bit.ly/hop9Fx

Arch Intern Med 2011.