The impact of COVID-19 sanitary measures on tuberculosis outbreaks

<bold>Background:</bold> Sanitary restrictions were legislated in Portugal in early 2020 as a response to the COVID-19 pandemic. These were hypothesised to lead to difficult-to-predict variations in tuberculosis (TB) incidence, as domestic contacts are prolonged and occupational and social exposures become rarer and shorter. <bold>Objective:</bold> To compare latent tuberculosis (LT) incidence before and following the implementation of the Portuguese sanitary restrictions during the COVID-19 pandemic. <bold>Methods:</bold> A prospective cohort study design was employed. Asymptomatic subjects aged >6 who had contacted for >8 cumulative hours with a patient with baciliferous pulmonary TB within the prior 15 days were screened for LT at the reference centre for TB in the Coimbra district, Portugal, over the course of 2 summer months in 2019 (n=113) and 2020 (n=82). Exclusion criteria included pregnancy, immunosuppression, SARS-CoV-2 vaccination, and prior mycobacterial infection or COVID-19. Screening was performed by tuberculin skin test (TST) (2 IU) and a diagnosis of LT was made for patients with positive TST and a subsequent positive IGRA. Use of face covers outside of home was recorded. <bold>Results:</bold> Adherence to face covers was invariable in the 2020 cohort and null in 2019. Positivity of TSTs was greater in 2020 (21.9% vs. 52.4%). For the subjects with positive TSTs, the incidence of latent tuberculosis in 2020 was inferior to that of 2019 (7.0% vs. 24.0%). <bold>Conclusions:</bold> Following legislation of sanitary measures for the COVID-19 pandemic in Portugal, increased rates of positive tuberculosis screenings were contrasted by a decrease in the diagnoses of LT, which may reflect a collateral protective effect on the rates of tuberculosis infection.