Assessment of tuberculosis contact investigation in Shanghai, China: An 8-year cohort study

Background Tuberculosis (TB) contact investigation has been observed as a useful programmatic tool in active case finding. We collected data of contact cases to evaluate the effectiveness of TB contact investigation programme in Shanghai, China. Methods Since 2009, we screened and followed up the close contacts of bacteria-positive TB cases in Songjiang, Shanghai and calculated the incidence of TB in close contacts and confirmed the transmission by genotyping and sequencing. Results A total of 4584 close contacts of 1765 contagious TB index cases were followed up for an average of 4 years. About 62 contacts (333/100 000, 95% CI: 256–428) developed TB excluding 6 co-prevalent cases. The contact cases consisted 1.50% (39/2592) of all the bacteria-positive cases in population. Transmission links were confirmed in 60% (9/15) familial contacts and 22% (2/9) in non-familial contacts. Source cases come from more than close contacts and both index and contact cases created other secondary cases in community. Conclusions Familial contacts are more likely to acquire TB from the index, indicating the priority of family members in TB contact investigation in China. However, most non-familial contacts were infected from sources in the community and contact cases attributed little to case finding in the TB-prevalent setting. Thus, active case finding should be strengthened in general population.