Tuberculosis infection and disease among schoolchildren: The influence of the HIV epidemic and of other factors

Background - The HIV/AIDS epidemic has caused an excess of tuberculosis cases in Spain and in other countries, but its impact on tuberculosis infection is less well understood. This study presents a massive screening undertaken to estimate the prevalence of tuberculous infection in a cohort of primary school entrants. The evolution of the risk of infection is studied by comparison with previous data in the same population. Methods - Tuberculin skin test screening with 2TU of PPD RT 23 of first grade students in the primary schools of Barcelona, in the 1994-95 school year (cohort born in 1988). Information was also sought from families of unscreened children. Contacts of PPD+ children were traced to locate index cases. The results were also linked to the case registry of the tuberculosis control programme. Results - The prevalence of tuberculin reactors free of BCG vaccination among the 11,080 schoolchildren screened belonging to the 1988 cohort was 0.76%. A 3% annual decline in the annual risk of infection is estimated by comparison with previous data. The identification of 24 cases with a previous history of tuberculosis disease and of 13 cases with active disease diagnosed after the screening was possible by the follow up of these tuberculin positive children and of the information provided by families of unscreened pupils. The screening detected 1.5 new cases of tuberculosis per 1000 tuberculin tests performed. Tuberculosis infection could be traced to HIV infected tuberculosis cases for at least 6% of the positive schoolchildren. Conclusions - The decline of the annual risk of infection continues in Barcelona, although at a slower pace than before the HIV/AIDS epidemic, probably attributable to the influence of injecting drug users with smear positive tuberculosis and HIV/AIDS.