Background: Genital ulcer disease including that caused by Herpes simplex virus type 2 (HSV-2) and syphilis facilitates sexual transmission of HIV-1. The effect of these infections on intra-partum mother-to-child-transmission (MTCT) of HIV-1 is unknown.
Methods: A case–control study was conducted using archived sera from HIV-1 positive women enrolled in ZVITAMBO, an MTCT trial. Cases were 509 women who transmitted HIV-1 to their infants intra-partum; controls were 1018 women whose infants remained uninfected at 12 months. Maternal serum collected at delivery, were tested for HSV-2 antibody. The 6-week post-partum sample was also tested for syphilis by RPR and TPHA to identify women with incubating or active syphilis at delivery. Rates of prevalent and incident HSV-2 and recently acquired syphilis were compared between cases and controls.
Findings: Overall prevalence of maternal HSV-2 and active syphilis at delivery were 82.5% [95% confidence interval (CI), 80.6–84.5] and 4.0% (95% CI, 3.0–5.1), respectively. Prevalent HSV-2 was associated with increased intra-partum MTCT [adjusted odds ratio (OR), 1.50; 95% CI, 1.09–2.08]. The proportion of intra-partum transmissions potentially attributable to prevalent HSV-2 infection was 28.4% (95% CI, 7.3–44.7). Maternal infection with active syphilis at delivery was not associated with intra-partum MTCT (unadjusted OR, 0.89; 95%CI, 0.49–1.59; adjusted OR, 0.64; 95% CI, 0.34–1.20).
Interpretation: HSV-2 infection is common among HIV-1-positive women and is associated with an increased risk of intra-partum MTCT. More than 25% of intra-partum MTCT may be attributable to maternal HSV-2 co-infection. Active maternal syphilis at the time of delivery is not associated with intra-partum MTCT risk.
From the aCentre for Sexual Health and HIV Research, Royal Free and University College Medical School, University College London, UK
bDepartment of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA
cZVITAMBO project, Harare, Zimbabwe
dVirology Section, CHRMC, Seattle, Washington, USA.
Received 8 November, 2006
Revised 17 August, 2007
Accepted 17 August, 2007
Correspondence to J. Humphrey, Zvitambo Study, 1 Borrowdale Road, Borrowdale, Harare, Zimbabwe. E-mail: firstname.lastname@example.org