TB outbreak investigation in a faith based boarding school: Challenges and control measures

Abstract

Background: Tuberculosis burden in UK is unacceptably high compared to similar countries. TB outbreaks in schools are extremely complex and present public health challenges. 7 cases of TB were notified at a faith based female boarding school in a UK city over 5 years. We aim to describe this challenging outbreak investigation. Methods & Materials: In 2008, the first pulmonary TB case was notified to public health authorities. In subsequent years, more cases were reported. Epidemiological investigations were undertaken in school including risk assessment, contact tracing and screening following each case to identify cases of active or latent TB. Mass screening at school was extremely challenging both in terms of logistics and managing cultural sensitivities. Initially, TB strain typing testing was not available. In 2013, following a case, the whole school was screened again. In early 2014, retrospective review and 24 loci TB strain typing was done to identify transmission chains. Results: From 2008 to 2013, mass TB screening was done four times in this school. In total, 1524 students and staff were screened. Of these, 98 had latent and 13 had active TB. In 2012, 64 cases (11%) had latent TB and 9 (1.6%) had active TB. Epidemiological investigations did not reveal any chains of transmission. TB strain typing in 2014 revealed that the 2012 case had identical 24 loci strain typing to the 2008 case. Strain typing was not possible in extra-pulmonary TB cases, and cases with missing loci could not be linked microbiologically. Conclusion: Strain typing data suggests ongoing TB transmission in school. Finding latent and active TB cases in school does not indicate exposure to notified cases, as most students are from a high risk population group. Whole genome sequencing could provide accurate data on ‘lineages’ of M. tuberculosis for evidence on chains of transmission. This outbreak highlights the need for innovative TB prevention and control strategies in such settings. Control measures included risk assessment and screening of new students, BCG vaccination history, prompt referral of symptomatic cases to TB services and raising awareness about TB. Proactive control measures in such high risk settings can minimise spread and prevent future outbreaks.