We conducted the first molecular study of tuberculosis (TB) to estimate the role of household contact and transmission from HIV-positive putative source contacts (PSCs) in a high HIV-prevalence area. TB patients in a long-term population-based study in Malawi were asked about past contact with TB. DNA fingerprinting was used to define clusters of cases with identical strains. Among 143 epidemiologically defined PSC-case pairs, fingerprinting confirmed transmission for 44% of household and family contacts and 18% of other contacts. Transmission was less likely to be confirmed if the PSC were HIV positive than if he or she was HIV negative (odds ratio 0.32, 95% confidence interval [CI] 0.14-0.74). Overall, epidemiologic links were found for 11% of 754 fingerprint-clustered cases. We estimate that 9%-13% of TB cases were attributable to recent transmission from identifiable close contacts and that nearly half of the TB cases arising from recent infection had acquired the infection from HIV-positive patients.
Crampin, A.C; Glynn, J.R.; Yates, M.D.; Mwaungulu, L.; Mwenebabu, M.; Chaguluka, S D; Floyd, S.; Drobniewski, F.; Fine, P.E.M.; Traore, H. Tuberculosis transmission attributable to close contacts and HIV status, Malawi. Emerging Infectious Diseases (2006) 12: 729-735.