Tuberculosis contact investigation in a rural state

The investigation of contacts of tuberculosis (TB) cases is an essential part of Mississippi's comprehensive TB program. A case interview is initiated within 24 hours, and the concentric circle method is used to identify and evaluate contacts. High-risk contacts of pulmonary cases are located and evaluated within 10 days. A follow-up evaluation is conducted by a TB consultant to determine the need for additional tests. All pulmonary contacts receive a 12-week follow-up tuberculin skin test (TST) if the initial test is negative. Directly observed treatment for latent TB infection (LTBI) is offered to all children aged <15 years, human immunodeficiency virus positive persons and others deemed at high risk for developing active disease. Mississippi contact investigations in 1990-1998 identified 212 (0.7%) cases of TB, and 5608 (17.5%) contacts with LTBI. In that period, the proportion of cases with contacts identified averaged 99%, with a mean number of contacts per case of 15.4. At the same time, 95% of contacts completed an evaluation for active TB and LTBI. Among contacts <15 years of age, >96% have completed LTBI treatment annually since 1992. Cases and case rates in Mississippi have decreased annually during this period. Effective TB contact investigation yields immediate results by identifying other sources of TB transmission and preventing future transmission through appropriate treatment of contacts with LTBI.