Spatial patterns of extensively drug-resistant tuberculosis transmission in KwaZulu-Natal, South Africa

BACKGROUND : Transmission is driving the global drug-resistant tuberculosis (TB) epidemic; nearly three-quarters of drug-resistant TB cases are attributable to transmission. Geographic patterns of disease incidence, combined with information on probable transmission links, can define the spatial scale of transmission and generate hypotheses about factors driving transmission patterns. METHODS : We combined whole-genome sequencing data with home Global Positioning System coordinates from 344 participants with extensively drug-resistant (XDR) TB in KwaZulu-Natal, South Africa, diagnosed from 2011 to 2014. We aimed to determine if genomically linked (difference of ≤5 single-nucleotide polymorphisms) cases lived close to one another, which would suggest a role for local community settings in transmission. RESULTS : One hundred eighty-two study participants were genomically linked, comprising 1084 case-pairs. The median distance between case-pairs’ homes was 108 km (interquartile range, 64–162 km). Between-district, as compared to within-district, links accounted for the majority (912/1084 [84%]) of genomic links. Half (526 [49%]) of genomic links involved a case from Durban, the urban center of KwaZulu-Natal. CONCLUSIONS : The high proportions of between-district links with Durban provide insight into possible drivers of province-wide XDR-TB transmission, including urban–rural migration. Further research should focus on characterizing the contribution of these drivers to overall XDR-TB transmission in KwaZulu-Natal to inform design of targeted strategies to curb the drug-resistant TB epidemic.Grants from the US National Institute of Allergy and Infectious Diseases (NIAID), National Institutes of Health (NIH): R01AI089349 (PI Gandhi and R01AI087465 (PI Gandhi). It was also supported in part by NIH/NIAID grants: K23AI083088 (PI Brust), K24AI114444 (PI Gandhi), K23AI134182 (PI Auld), Emory CFAR P30AI050409 (PI Curran), Einstein CFAR P30AI051519 (PI Goldstein), by Einstein/Montefiore ICTR UL1 TR001073 (PI Shamoon).https://academic.oup.com/jid2019-12-15hj2019Medical Microbiolog