The role of neighborhood factors in the cumulative number of episodes of recurrent tuberculosis in Cape Town

Recurrent tuberculosis (TB) accounts for 30% of the annual TB burden in Cape Town. To better understand mechanisms behind recurrences, we assessed the association between neighborhood factors and the cumulative number of TB episodes per individual between 2003 and 2015. We used TB notification data, previously geocoded, and probabilistically linked with 2011 Census data at the neighborhood level. Individuals were grouped by follow-up time after their first TB episode: 5-10 years (FUT5-10) and over 10 years (FUT10+). Ordinal regressions adjusted for age and sex examined associations, with robust standard errors for neighborhood clustering. A secondary analysis from 2009 onward included HIV status, restricted to individuals with at least five years of follow-up. In the FUT10+ cohort, 9.6% had two TB episodes and 2.1% had three or more; this was 7.9% and 1.3% in FUT5-10, and 7.4% and 1.3% in the secondary analysis cohort (SAC). A higher cumulative number of episodes was associated with neighborhood household size across cohorts (FUT10+ aOR = 1.23 (95% CI 1.15-1.31), FUT5-10 aOR = 1.26 (95% CI 1.16-1.37), annual neighborhood TB incidence (FUT10+ aOR = 1.13 (95% CI 1.06-1.20), FUT5-10 aOR = 1.11 (95% CI 1.04-1.19)), neighborhood socioeconomic index (FUT10+ aOR = 0.98 (95% CI 0.95-1.01), FUT5-10 aOR = 0.94 (95% CI 0.91-0.97), SAC aOR = 0.93 (95% CI 0.88-0.98)) and HIV infection (SAC aOR = 1.83 (95% CI 1.59-2.10)). These findings highlight that neighborhood-level risk factors contribute to recurrence and suggest the role of reinfection in recurrent TB. Targeting neighborhoods with high TB incidence, larger households, and lower socioeconomic status may improve screening and reduce TB burden in Cape Town.