Previous studies suggest that most injection drug users become infected with Hepatitis C virus and Hepatitis B virus soon after initiating drug use.
The Urban Health Study recruited serial cross-sections of injection drug users in the San Francisco Bay area from 1986 to 2005.
Dr Thomas O'Brien and colleagues from the USA determined the prevalence of antibody to Hepatitis C virus and Hepatitis B virus among Urban Health Study participants during 1998 to 2000.
The team examined whether the time from onset of injection to acquisition of viral hepatitis has increased.
|34% of recent initiates had shared syringes during 1998 to 2000|
The research team also compared the findings among recent initiates to drug use who participated during 1998 to 2000 with those who participated in 1987.
Of 2,296 injection drug users who participated during 1998 to 2000, 91% had antibody to Hepatitis C virus and 81% to Hepatitis B virus.
The team found that the number of years a person had injected drugs strongly predicted infection with either virus.
The research team noted that Hepatitis C virus seroprevalence among recent initiates in 1998 to 2000, by years of injection drug use, was 47% for less than 2 years, 72% for 3 to 5 years, 71% for 6 to 9 years.
By comparison, Hepatitis C virus seroprevalence among 1987 participants was 76% for less than 2 years, 86% for 3 to 5 years, and 91% for 6 to 9 years.
The researchers observed a consistent pattern for Hepatitis B virus.
The team reported that these findings were not explained by demographic differences between 1987, and 1998 to 2000 participants.
During 1987, however, 59% of recent initiates had shared syringes within the past 30 days compared with 34% during 1998 to 2000.
Dr O'Brien's team concluded, "Hepatitis C virus and Hepatitis B virus seroprevalence among newer initiates to injection drug use in the San Francisco Bay area decreased markedly between 1987, and 1998 to 2000."
"This decrease coincided with the implementation of prevention activities among this population."