Hepatitis C Cases Mysteriously Plunge 80% : Health: Scientists at L.A. conference say they have not found a change in behavior among drug abusers, the main group affected by the virus.
The incidence of new hepatitis C infections among intravenous drug abusers has dropped unexpectedly by a dramatic 80% since 1990, according to preliminary results from the Centers for Disease Control and Prevention.
Transmission of the virus among drug abusers is thought to account for as much as 85% of the hepatitis C infections discovered each year--a number that totaled 150,000 in 1990.
But data from the CDC’s Sentinel Surveillance Program, designed to detect shifts in infectious disease rates, indicates that the infection rate is falling sharply, Dr. Harold Margolis, chief of CDC’s hepatitis branch, told a special hepatitis meeting convened Friday in Los Angeles by the American Gastroenterological Assn.
Although the preliminary results, at first blush, suggest that recent efforts to prevent the spread of disease among drug abusers are having a positive effect, CDC researchers have been unable to detect any specific changes in behavior that might account for the decline.
Even more perplexing, the drop in hepatitis C transmission is not accompanied by a corresponding drop in HIV transmission among drug abusers. In fact, Margolis said, recent data suggests that the HIV transmission rate is rising once again in that high-risk group. “We need to go back in (among drug abusers) and see what is going on,” Margolis said.
One possibility, experts said, is that behavioral change programs directed at drug abusers may have a greater initial effect on hepatitis C because the virus that causes it is slightly more difficult to transmit than HIV, and thus more susceptible to intervention programs. Another possibility is that there are far fewer casual users of intravenous drugs now than in the 1980s (and that most hard-core users have already contracted the virus).
Prevention programs are particularly important because the possibility of developing a vaccine against the virus in the near future is bleak, said Dr. Eugene R. Schiff of the University of Miami School of Medicine, a co-chairman of the conference. The consensus development conference also concluded that hepatitis C should be treated more aggressively and for longer periods, and that new combinations of drugs should be tested as soon as possible.
The hepatitis C virus is the most common of five distinct hepatitis viruses, labeled A through E, that cause inflammation of the liver, cirrhosis and liver cancer. It is a major public health problem throughout the world.
An estimated 1.3% of the U.S. population, nearly 3.5 million people, are chronically infected by the hepatitis C virus. Hepatitis is the ninth leading cause of death in the United States, killing about 10,000 people each year, and the leading cause of liver failure leading to transplantation.
The hepatitis C virus was discovered only six years ago by researchers at Chiron Corp. in San Francisco. Before that time, the disease was known only as “non-A, non-B hepatitis,” and transfusions were a major cause of infection. New screening tests for blood have eliminated that threat, but the virus is also transmitted by tattoo needles, body-piercing jewelry and sexual relations.
The lone effective treatment for hepatitis C infection is a six-month regimen of the genetically engineered protein interferon alfa-2b, but only about 15% to 20% of those receiving the drug undergo a long-term remission. New results indicate that the remission rate can be doubled if treatment extends over a 12-month period, Schiff said, and the conference strongly recommended that all patients receiving the drug undergo the new regimen.
The conference members also urged drug companies to accelerate combination trials of anti-hepatitis drugs. The antiviral agent ribavirin, for example, has not been shown to benefit hepatitis C patients when used alone. But pilot studies combining it with interferon suggest that the two drugs together may produce a remission in 40% of patients who do not respond to interferon alone. The bleakest news involved efforts to develop a vaccine against hepatitis C. Several studies have shown that humans and animals develop antibodies against the virus, but it has now become clear that the virus can undergo dramatic mutations within an infected individual so that the immune system no longer recognizes it.
