AEGiS-14IAC: Mobility is an important risk factor for HIV infection in rural Tanzania.

14th International AIDS Conference

Barcelona, Spain - July 7-12, 2002

Mobility is an important risk factor for HIV infection in rural Tanzania.

Int Conf AIDS 2002 Jul 7-12; 14:(abstract no. ThOrC1485)

Isingo R, Urassa M, Kishamawe C, Knoops E, Voeten H, Mwaluko G, Boerma T, Zaba B
TANESA, Mwanza, Tanzania

BACKGROUND: Mobility facilitates sexual mixing and is considered a key risk factor in the spread of HIV, but few studies assess incidence effects. Data from a longitudinal community-based study in Kisesa ward, Mwanza region are used to measure its direct contribution to HIV infection.

METHODS: Socio-demographic characteristics, sexual partnership information and HIV status collected for 11,340 persons in 1994/5, 1996/7 and 1999/0 were linked to migration histories from 13 rounds of demographic surveillance between 1994 and 2000. Incidence estimates are based on 21,728 person-years of observation contributed by 5,647 individuals aged 15-49 tested at least twice. Hazard analysis with time varying co-variates is used to assess the impact of mobility on incidence.

RESULTS: Overall 58% of men and 70% of women changed residence at least once; for those with two HIV tests mobility rates were 50% and 61% respectively. Among the mobile 61% of men and 25% of women reported non-marital sexual partnerships, compared to 50% and 12% respectively for non-movers. 270 sero-converters were identified, yielding an overall annual incidence of 1.2% (confidence limits 1.1-1.4). Incidence was significantly higher in mobile individuals: 1.8% (1.6-2.1), than for non-movers: 0.6% (0.5-0.8). Restricting mobility to movement occurring before sero-conversion, and allowing for time variant effects of risk factors such as age, marital status, place of residence and male circumcision, suggests that mobility per se significantly increases the risk of HIV infection, with hazard ratios of 5.1 (3.5-7.5) for males and 4.9 (3.5-7.5) for females independent of the excess risk associated with non-marital partnerships, for which male and female hazard ratios were 2.3 (1.3-2.7) and 2.2 (1.5-3.2).

CONCLUSION: Mobility is associated with sexual partnership formation and substantially increased HIV infection rates. Incomplete reporting of non-marital partnerships may complicate risk attribution.

Keywords: AEGIS, Tanzania, Risk Factors, HIV Infections, Incidence, HIV Seropositivity, Marital Status, Demography, Residence Characteristics, Family Characteristics, Emigration and Immigration, Longitudinal Studies, Greece, Human, Female, Male

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ThOrC1485