A summary of contact tracing incident investigation outcomes in congregate settings from a large UK city over a 7-year period

Abstract

Background: Mycobacterium tuberculosis (TB) is a respiratory droplet spread bacterial disease. Exposure can result in a latent state with subsequent active infection. Contact tracing aims to identify these infected contacts. The outcomes of contact investigations following incidents in congregate settings are described for a large UK city over a 7-year period.

Methods: Utilising public health data from a large UK ethnically diverse urban population as part of active case investigations in non-household settings, we describe the outcomes of large scale contact tracing investigations.

Results: Over 7 years, 167 incidents were investigated generating 8091 contacts. 112 settings were involved demonstrating recurrent events due to non-identified tracing opportunities in 45 settings. Nearly half of index cases were from the UK (49.7%). Casual contacts demonstrated active disease in 26.8% of cases, more than close contacts (19.5%) in congregate settings. 3.6% had multidrug resistant TB and 30.8% were smear negative, smear positive status generating 5 times more disease detected in contacts.

Conclusion: Conventional contact tracing approaches in congregate settings generate large contact groups with low disease detection. A more nuanced approach that identifies relationships and exposures might help to improve the efficiency of contact tracing.