P155 A high rate of tuberculosis transmission in a food (meat processing) factory setting? Investigation into a long running tuberculosis cluster in the UK and the interventions deployed in response

<h3></h3> Between 2011 and 2019, 10 tuberculosis (TB) cases were linked to a cluster via strain typing and/or whole genome sequencing. Four further cases were identified in quick succession at the end of 2019 into early 2020. Overall, 13 of the cases had either pulmonary or pulmonary and extrapulmonary TB and 8 cases had confirmed or suspected links to a food factory. In response an Incident Management Team recommended mass TB screening with the aim of identifying active and latent TB cases to break chains of transmission. Populations most at risk of TB exposure were identified and invited for screening at the factory. Blood samples were taken to test for TB infection (IGRA) and demographic, symptoms and TB exposure information collected via a questionnaire. Following high positive IGRA results a second round of screening was offered including onsite chest-x-rays. Based on the screening results, individuals were either discharged or referred to local TB services for follow up. The screening questionnaires information was combined with the blood test and chest-x-rays results. 135 individuals were screened in the first round. Overall IGRA positivity was 54.1%, with 41.2% in the UK born population versus 58.4% in the non-UK born. All IGRA positive individuals were referred for further investigating along with 9 due to symptom history. 348 people attended the second round of screening. 95% had chest-x-rays and 91% blood tests of which 22% were IGRA positive. Overall, 11.6% in the UK born population were positive compared to 25.3% in the non-UK born. Twelve individuals were referred for clinical review/further assessment due to abnormal chest x-rays. One new active TB case was identified and commenced on treatment. The IGRA positivity levels found in the first round of screening at the factory suggested TB transmission in this cohort particularly evidenced by high levels in the UK born population. In response screening was expanded and subsequently showed lower positivity suggesting the groups most at risk were correctly targeted in the first screening round. The screening enabled many factory workers with latent TB to be identified and offered treatment to break the cycle of disease transmission.