Mobility and HIV transmission across three urban communities in Zambia: using qualitative data to interpret phylogenetics in a mixed methods analysis of HPTN 071 (PopART) data


BACKGROUND: Population mobility (permanent resettling, transient and circular movements) between neighbourhoods contributes to HIV transmission. This analysis uses qualitative research describing mobility factors to understand phylogenetics data estimates of HIV transmission patterns within and across three of nine HPTN 071-02 (PopART Phylogenetics) study sites in southern Zambia, selected based on socio-economic linkages between communities located in adjacent districts and with high HIV incidence.
METHODS: Qualitative data originated from formative research (2013), study and intervention uptake documentation (2014'2018) and a qualitative cohort of 13 individuals in one community (2017-2018). Data were analysed using thematic and narrative approaches describing factors influencing mobility. Blood samples were collected from HIV-positive individuals at health facilities and in the community between 2016-2018. HIV sequences were identified by whole-genome viral sequencing. Phylogenetic analysis identified likely transmission pairs in which at least one partner was enrolled in one of the three study communities.
RESULTS: Qualitative findings showed that cross-border trading, tourism and labour migration contributed to mobility in all three communities. Two communities are in a tourist area near international borders, promoting cross-border trading and in-migration from tourists and transient groups, including female sex workers and cross-border traders. Labour migration (both temporary and permanent) between two adjacent districts increased in 2012 when the provincial capital was relocated. Temporary migration linked to trading in farm products and seasonal migration linked to fish and charcoal trading was common across the three communities. HIV sequences were obtained from 1,340 women and 773 men, aged 18-79 (709, 569 and 835 sequences from respective communities). Phylogenetic analysis identified 108 transmission pairs, in which at least one individual in the pair was from one of the three communities. Of these, 87 (80.6%) occurred within the same communities, while 21 (19.4%) occurred between different communities.
CONCLUSIONS: Mobility centred on livelihood options may contribute to HIV transmission across these three study communities. HIV prevention efforts with mobile populations are critical to manage HIV-infections locally. Future mixed methods research could have a stronger focus on mobility and socio-economic characteristics of individuals in sexual relationships to provide insights on HIV transmission.

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