Reusable needles--a major risk factor for acute virus B hepatitis.

We conducted a case control study to find the extent to which acute virus B hepatitis was hospital acquired. One hundred and sixty consecutive cases of acute virus B hepatitis were compared with age (+/- 3 years) and sex matched healthy hospital visitors. Exposure to reusable needles, blood or blood products, therapeutic and diagnostic procedures, common razors and sexual practices were elicited by means of a questionnaire. Only exposures in the incubation period (6 weeks to 6 months before the onset of symptoms) were included in the analysis. The odds ratio (OR) for injections for reusable needles was 6.3 [95% confidence interval (CI) = 3.8-10.6]. The OR for single injection (OR = 3.9; 95% CI = 2.0-7.3) was less than that for multiple injections (OR = 9.8; 95% CI = 3.8-26.3), showing a dose response relationship. The proportion of cases of acute virus B hepatitis attributable to hospital related exposures was 67%. Proper aseptic techniques and sterilization practices can substantially reduce the incidence of acute hepatitis B in the population.