The annual risk of tuberculous infection in Orissa State, India.

SETTING: Rural and urban areas of eight selected districts of Orissa State, India.

OBJECTIVES: To estimate the average annual risk of tuberculous infection (ARTI) in the state.

DESIGN: A community-based, cross-sectional tuberculin survey was conducted among children aged 1-9 years residing in a sample of rural and urban areas of eight districts of Orissa State. A stratified sampling was adopted for selection of clusters. Highly trained designated tuberculin testers administered 0.1 ml (1 TU) of PPD RT 23 with Tween 80 by the Mantoux method to 10 626 children. Transverse tuberculin reaction sizes were measured about 72 h later by trained designated tuberculin readers. The number of children satisfactorily test-read was 10 191.

RESULTS: Based on the frequency distribution of tuberculin reaction sizes, the average ARTI in the state was estimated at 1.7-1.8%. The children residing in urban areas were observed to be at a significantly higher risk of infection than those in rural areas.

CONCLUSION: The study in Orissa State suggests high rates of transmission of tuberculous infection and calls to attention the need for intensification of concerted and sustained tuberculosis control efforts.