Pulmonary tuberculosis infection among workers in the informal public transport sector in Lima, Peru

Background: Because a strong association was observed between pulmonary tuberculosis (TB) and the use of public transport, increasing with duration of journey, a study was carried out to assess infection by Mycobacterium tuberculosis and working conditions among workers in this sector. Methods: A cross-sectional study was conducted between June and September 2008. A total of 104 workers from two public transport minibus ('combi') cooperatives covering marginal areas of the Ate-Vitarte district in Lima were interviewed. Demographic and occupational details were collected as well as prior family and personal history of TB and BCG vaccination. The tuberculin skin test (TST) was administered to each study subject and an induration of ≥10 mm was considered positive. Statistical analysis was based on logistic models, ORs and their 95% CIs. Results: TST results were obtained for 70.2% (n=73), of whom 76.6% (n=56) were positive. Positivity was significantly associated with those who had worked for more than 2 years (crude OR 11.04; 95% CI 3.17 to 38.43) and more than 60 h/week (crude OR 9.8; 95% CI 2.85 to 33.72). These associations remained significant in a multivariate model as well. Conclusion: The association observed between years of working and weekly work burden among minibus workers suggests an occupational risk in service jobs in low-income countries with high TB prevalence. Consequently, other types of users are at increased risk for TB infection, with a causal relationship between effect and duration of exposure.