Prevalence and determinants of hepatitis A virus exposure among prison entrants in Queensland, Australia: implications for public health control.

In September 1997, a multicentre outbreak of hepatitis A virus (HAV) infection occurred in the Queensland prison system following a prolonged community-based HAV epidemic among illicit drug users. As part of the public health response, a cross-sectional survey was undertaken to estimate the sero-prevalence of, and identify the determinants for, recent and past HAV infection among the incoming male prisoner population. Exposure data were collected through face-to-face interviews with 214 consenting inmates, whose sera were screened for immunoglobulin G (IgG) and immunoglobulin M (IgM) antibodies to HAV. Overall, 81 (37.9%) inmates were HAV-IgG seropositive, and four inmates were HAV-IgM seropositive, HAV-IgG seropositivity was strongly associated with year of birth (age) (Ptrend < 0.0001), being born outside Australia (relative risk (RR) 1.9, 95% CI 1.4-2.7) and being of a non-English speaking background (RR 2.5, 95% CI 1.7-3.7). Lifestyle exposures (such as occupation, overseas travel and illict drug use) were not associated with an increased risk of HAV-IgG seropositivity. In contrast, all four HAV-IgM seropositive inmates were English-speaking, Australian-born males who used illicit drugs. These findings suggest that the risk factors for recent and past HAV infections among prisoners differ, with implications for HAV control in correctional settings. Strategies for HAV prevention, including routine screening of inmates and vaccination of susceptibles, are considered in the context of current models of disease transmission.