Contacts of tuberculosis patients in high-incidence countries.

The risk of acquiring infection with Mycobacterium tuberculosis correlates with duration of exposure to an infectious source of tuberculosis. Contact identification is therefore a comparatively high-yield activity. However, in resource-poor settings tuberculin is rarely available, and even where it is available, non-specific cross-reactions to tuberculin resulting from BCG vaccination complicate the interpretation of tuberculin test results. The identification of a putative infection with M. tuberculosis in a contact must result in intervention. Excluding active tuberculosis is mandatory before preventive therapy is provided. This might prove difficult in areas where the most and often only affordable diagnostic means is microscopy. The International Union Against Tuberculosis and Lung Disease (IUATLD) has thus proposed to target preventive therapy to healthy children below the age of 5 years living in the same household as a sputum smear-positive tuberculosis case, with the sole recourse to clinical contact examination. While this approach will lead to treatment of a considerable proportion of uninfected children, the advantages are several-fold: first, these are the easiest identifiable contacts; second, they are particularly prone to progression to disease if infected; third, emerging drug resistance is of little concern at that age; fourth, administration of preventive treatment can be delegated to the source case. This approach is safe, simple, and affordable.