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.