TB surveillance in correctional institutions in Hong Kong, 1999-2005

OBJECTIVE: To understand the epidemiology of tuberculosis (TB) inside the prison system of Hong Kong. METHOD: Prospective territory-wide TB surveillance was conducted among prisoners in 24 correctional institutions. RESULTS: From 1999 to 2005 622 prevalent TB cases diagnosed before or within 3 months of incarceration and 214 incident cases diagnosed after 3 months were reported by prison staff to a paper-based central prison TB registry. Both crude prevalence and incidence were falling (chi(2) for trend both P < 0.001) despite a higher sex- and age-adjusted prison TB incidence as compared to the general population (indirectly standardised rate [ISR] 280.6 vs. 108.0/100000 P < 0.001). Illegal immigrants (odds ratio [OR] 3.6 95% confidence interval [CI] 1.8-7.4) and drug addicts (OR 2.04 95%CI 1.13-3.7) were two major risk groups. The TB incident risk disappeared after their exclusion (ISR 117.1 vs. 108.0/100000 P = 0.52). No significant difference in the multidrug-resistant rate was foundwhen comparing the group with the general population (3.5% vs. 1.0% OR 3.6 95%CI 0.5-28.4). No extensively drug-resistant (XDR) cases were identified. CONCLUSION: TB remains a significant disease in local prisons. Further strengthening of TB control programmes in prisons especially targeting the higher risk groups is recommended.