Back-to-Africa introductions of Mycobacterium tuberculosis as the main cause of tuberculosis in Dar es Salaam, Tanzania.

Zwyer, Michaela; Rutaihwa, Liliana K; Windels, Etthel; Hella, Jerry; Menardo, Fabrizio; Sasamalo, Mohamed; Sommer, Gregor; Schmülling, Lena; Borrell, Sonia; Reinhard, Miriam; Dötsch, Anna; Hiza, Hellen; Stritt, Christoph; Sikalengo, George; Fenner, Lukas; De Jong, Bouke C; Kato-Maeda, Midori; Jugheli, Levan; Ernst, Joel D; Niemann, Stefan; ... (2023). Back-to-Africa introductions of Mycobacterium tuberculosis as the main cause of tuberculosis in Dar es Salaam, Tanzania. PLoS pathogens, 19(4), e1010893. Public Library of Science 10.1371/journal.ppat.1010893

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In settings with high tuberculosis (TB) endemicity, distinct genotypes of the Mycobacterium tuberculosis complex (MTBC) often differ in prevalence. However, the factors leading to these differences remain poorly understood. Here we studied the MTBC population in Dar es Salaam, Tanzania over a six-year period, using 1,082 unique patient-derived MTBC whole-genome sequences (WGS) and associated clinical data. We show that the TB epidemic in Dar es Salaam is dominated by multiple MTBC genotypes introduced to Tanzania from different parts of the world during the last 300 years. The most common MTBC genotypes deriving from these introductions exhibited differences in transmission rates and in the duration of the infectious period, but little differences in overall fitness, as measured by the effective reproductive number. Moreover, measures of disease severity and bacterial load indicated no differences in virulence between these genotypes during active TB. Instead, the combination of an early introduction and a high transmission rate accounted for the high prevalence of L3.1.1, the most dominant MTBC genotype in this setting. Yet, a longer co-existence with the host population did not always result in a higher transmission rate, suggesting that distinct life-history traits have evolved in the different MTBC genotypes. Taken together, our results point to bacterial factors as important determinants of the TB epidemic in Dar es Salaam.

Item Type:

Journal Article (Original Article)


04 Faculty of Medicine > Pre-clinic Human Medicine > Institute of Social and Preventive Medicine (ISPM)

UniBE Contributor:

Fenner, Lukas, Ballif, Marie, Egger, Matthias


600 Technology > 610 Medicine & health
300 Social sciences, sociology & anthropology > 360 Social problems & social services




Public Library of Science


[4] Swiss National Science Foundation ; [18] European Research Council




Pubmed Import

Date Deposited:

05 Apr 2023 09:27

Last Modified:

27 Apr 2023 09:13

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