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Who infects whom? HIV-1 concordance and discordance among migrant and non-migrant couples in South Africa

Lurie, Mark Na,b; Williams, Brian Gc; Zuma, Khangelania,d; Mkaya-Mwamburi, Davida; Garnett, Geoff Pe; Sweat, Michael Df; Gittelsohn, Joelf; Karim, Salim SAbdoolg

Epidemiology & Social

Objectives: To measure HIV-1 discordance among migrant and non-migrant men and their rural partners, and to estimate the relative risk of infection from inside versus outside primary relationships.

Design: A cross-sectional behavioural and HIV-1 seroprevalence survey among 168 couples in which the male partner either a migrant, or not.

Methods: A detailed questionnaire was administered and blood was collected for laboratory analysis. A mathematical model was developed to estimate the relative risk of infection from inside versus from outside regular relationships.

Results: A total of 70% (117 of 168) of couples were negatively concordant for HIV, 9% (16 of 168) were positively concordant and 21% (35 of 168) were discordant. Migrant couples were more likely than non-migrant couples to have one or both partners infected [35 versus 19%; P = 0.026; odds ratio (OR) = 2.28] and to be HIV-1 discordant (27 versus 15%; P = 0.066; OR = 2.06). In 71.4% of discordant couples, the male was the infected partner; this did not differ by migration status. In the mathematical model, migrant men were 26 times more likely to be infected from outside their regular relationships than from inside [relative risk (RR) = 26.3; P = 0.000]; non-migrant men were 10 times more likely to be infected from outside their regular relationships than inside (RR = 10.5; P = 0.00003).

Conclusions: Migration continues to play an important role in the spread of HIV-1 in South Africa. The direction of spread of the epidemic is not only from returning migrant men to their rural partners, but also from women to their migrant partners. Prevention efforts will need to target both migrant men and women who remain at home.

From the aSouth African Medical Research Council, HIV Prevention and Vaccine Research Unit, Durban South Africa, the bDepartment of Infectious Disease, Brown University School of Medicine, and the Miriam Hospital, Providence USA, c16 rue de la Canonniere, Geneva, Switzerland, the dDepartment of Statistics, University of Waikato, Hamilton, New Zealand, eDepartment of Infectious Disease Epidemiology, Imperial College School of Medicine at St. Mary's, London, UK, the fDepartment of International Health, Johns Hopkins University School of Public Health, Baltimore USA and the gUniversity of Natal, Durban South Africa.

Correspondence to Mark Lurie, PhD, Assistant Professor of Medicine and Community Health (Research), Brown University School of Medicine and the Miriam Hospital, 164 Summit Avenue, Providence, Rhode Island 02906 USA. Tel: +1 401 793 4397; fax: +1401 793 4907; e-mail: Mark_Lurie@brown.edu

Received: 8 March 2002; revised: 17 April 2003; accepted: 8 May 2003.

© 2003 Lippincott Williams & Wilkins, Inc.