Injection drug users are still at a very high risk of acquiring hepatitis C (HCV) and hepatitis B (HBV); however, needle-sharing is less common, and users do not become infected as quickly as they did in the past, according to a new study.
Both HCV and HBV raise the risk of liver cancer and other life-threatening liver disease and past studies have shown that most injection drug users became infected with both viruses soon after they take up the habit. To address this danger, groups have implemented interventions such as needle exchange programs for at-risk populations.
Recently, researchers sought to determine what effect such interventions may have had, by determining the current prevalence and patterns of acquisition of those diseases among injection drug users. The investigation was led by Fan-Chen Tseng and Thomas R. O'Brien of the National Cancer Institute, and Brian R. Edlin of Weill Cornell Medical College's Center for the Study of Hepatitis C and the former Director of the Urban Health Study at the University of California, San Francisco.
They used data from the Urban Health Study, which recruited injection drug users in the San Francisco Bay area from 1986 to 2005. That study collected demographic information along with blood samples which were analyzed for seroprevalence of blood-borne infections. Tseng and colleagues focused on HCV and HBV antibody prevalence in users who participated between 1998 and 2000 and compared them to those of users who participated in 1987.
Of the 2,296 drug users included in the Urban Health Study between 1998 and 2000, 91 percent had antibody to HCV and 80 percent to HBV. However, those who had recently started injecting drugs had far lower rates. Only 47 percent of participants who had been injecting drugs for less than two years were infected with HCV, compared to 71 percent who had been using for 6-9 years. Comparable rates among the 1987 population were 76 percent and 91 percent.
For HBV, about 5 percent of the population had serologic evidence of vaccination against the virus. Among the others, 41 percent of those who had injected drugs for less than 2 years, and 57 percent of those who had been using for 6-9 years were infected. Comparable rates among the 1987 population were 45 percent and 80 percent.
Only 34 percent of the participants from 1998-2000 said they had shared syringes in the past 30 days, compared to about 59 percent who had done so in 1987.
Although the population examined in this study was not a random sample, and the authors had no way to pinpoint the reasons for the improvements over time, the reductions in infection rates the authors observed coincided with the institution of street-based outreach, HIV counseling and testing, and needle exchange programs.
The findings suggest that there is now a longer window of opportunity for interventions among this at-risk population. To reduce infection rates further, the authors suggest, it is also of paramount importance to reduce the number of people who start injection drug use and to make substance abuse treatment available to those who wish to stop.
The authors conclude, "It is encouraging that the frequency of HCV and HBV appears to have decreased markedly among new initiates to injection drug use in the San Francisco Bay area. If the reductions in the prevalence of these infections can be sustained, the risk of end stage liver disease and liver cancer should decrease in this population."
Reference: "Seroprevalence of Hepatitis C Virus and Hepatitis B Virus Among San Francisco Injection Drug Users, 1998-2000." Tseng, Fan-Chen; O'Brien, Thomas; Zhang, Mingdong; Kral, Alex; Ortiz-Conde, Betty; Lorvick, Jennifer; Busch, Michael P.; Edlin, Brian. Hepatology; September 2007; (DOI: 10.1002/hep.21765).
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