Programs that give injection drug users clean needles or safer drug substitutes may help cut their odds of contracting the liver infection hepatitis C, a new study suggests.

The hepatitis C virus is passed through contact with infected blood. Health care workers are particularly vulnerable, as are people who get tattoos in unclean environments. But in the U.S., most of the roughly 18,000 new infections each year occur when people who inject opiates, like heroin, share tainted needles or syringes.

Studies have found that clean-needle programs do reduce needle-sharing, and they seem to curb drug users' risk of infection with HIV, the virus that causes AIDS. The same appears true of programs that get addicts into treatment with opiate "substitutes" like methadone, which is taken orally instead of injected.

But there has been little evidence that these programs help cut the spread of hepatitis C.

A problem with the hepatitis C virus is that it's much easier to transmit than HIV. Even a faint amount of blood on a shared needle, for example, might be enough to infect another person.
But the new findings, published in the journal Addiction, suggest that needle and opiate-substitution programs can make a difference in hepatitis C risk, according to senior researcher Matthew Hickman, a professor of public health at the University of Bristol in the UK.

Combining the results from six previous studies of UK programs, Hickman's team found that drug users with the highest "coverage" from clean-needle programs were about half as likely to contract hepatitis C as other users.

Among users who said they got enough clean needles to cover all of their injections, just under 4 percent tested positive for hepatitis C during the studies, which lasted up to a year. That compared with 7 percent of drug users who didn't get clean needles for all their injections.

Similarly, the rate of new hepatitis C infection was 3 percent among drug users who were currently taking an opiate substitute (usually oral methadone), versus 7 percent among those not on treatment.

Drug users participating in both types of programs fared best of all, with a new infection rate of 2 percent.

"The implication is that hepatitis C transmission can be reduced by opiate substitution therapy and needle and syringe programs, especially their combination," Hickman told Reuters Health in an email.

While the study looked only at UK programs, it's likely the results would be similar in other countries, he said.

The study has its limits. It combined the results of several observational studies, where researchers "observed" groups of injection drug users who chose to use or not use the needle and opiate substitution programs.

Leaving the choice to the individual makes it hard to show that the programs are what caused hepatitis C infection rates to go down. There may be other differences between people who used the programs and those who didn't that would explain the results.

The findings are also based on small numbers, Hickman's team points out. The researchers had usable information on 919 program participants across the six study sites, and there were 40 cases of new hepatitis C infection.

Still, Hickman said the study starts to fill a gap in the knowledge of how well injection drug use programs are working.

In the U.S., new cases of hepatitis C infection have fallen sharply since the 1980s, according to Centers for Disease Control and Prevention. In the early 1990s, doctors found a way to detect the virus in blood, which meant they could make sure it wasn't transmitted in blood transfusions.

But chronic hepatitis C infection, the agency says, remains a major public health problem.

Between 75 and 85 percent of people infected with hepatitis C develop chronic infection, which can eventually cause serious liver diseases like cirrhosis (scarring of the liver) and liver cancer. Hepatitis C presently accounts for about a third of the liver transplants done in the U.S. each year.

An estimated 3.2 million Americans have chronic hepatitis C, about half of whom are unaware of it. (The initial infection most often causes no symptoms.)

There are medications for treating chronic hepatitis C, although they are not effective for everyone and have side effects like fatigue, nausea, headache and sleep problems.

According to Hickman, one question for future studies is whether treating chronic hepatitis C in injection drug users helps reduce transmission.