The role of tuberculosis symptoms in transmission risk to cell contacts in prisons.

Background: Understanding determinants of transmission is critical to devising effective strategies to reduce its burden. Whether and to what extent symptoms influence transmission remains poorly understood.

Methods: Between 2020 and 2022, we systematically screened PDL from three prisons in Brazil for TB by symptom assessment and sputum testing with Xpert MTB/RIF Ultra. We performed QuantiFERON-TB Gold Plus (QFT) testing among cell contacts of individuals with TB and in cells with no TB case identified. We evaluated the relationship between TB exposure (symptomatic, asymptomatic, none) and QFT positivity using Bayesian generalized linear mixed models.

Results: We screened 7641 PDL for TB and identified 290 cases, yielding a prevalence of 3.8% (290/7641). After applying exclusion criteria, 686 participants were included for QFT analysis: 132 contacts of 42 individuals with symptomatic TB, 224 individuals exposed to 52 individuals with asymptomatic TB; 330 individuals with no recent cell exposure. Odds of QFT positivity were higher in symptomatic (adjusted odds ratio [aOR] 2.50, 95% CrI 1.51-4.16) and asymptomatic (aOR 1.61, 95% CrI 1.06-2.45) exposure groups compared to those unexposed. QFT positivity in contacts of symptomatic and asymptomatic TB did not differ (aOR 1.56, 95% CrI 0.92-2.63).

Conclusions: Over half of individuals with TB lacked symptoms, and their contacts had increased risk of QFT positivity-comparable to contacts of symptomatic TB-compared with individuals without recent cell exposure. These findings underscore the importance of systematic screening for TB, irrespective of symptoms, to accelerate diagnosis and prevent transmission in high-burden settings.