Objectives: To compare the impact of single-round mass treatment of sexually transmitted diseases (STD), sustained syndromic treatment and their combination on the incidence of HIV in rural Africa.
Methods: We studied the effects of STD interventions by stochastic simulation using the model STDSIM. Parameters were fitted using data from a trial of improved STD treatment services in Mwanza, Tanzania. Effectiveness was assessed by comparing the prevalences of gonorrhoea, chlamydia, syphilis and chancroid, and the incidence of HIV, in the general adult population in simulations with and without intervention.
Results: Single-round mass treatment was projected to achieve an immediate, substantial reduction in STD prevalences, which would return to baseline levels over 5–10 years. The effect on syphilis was somewhat larger if participants cured of latent syphilis were not immediately susceptible to re-infection. At 80% coverage, the model projected a reduction in cumulative HIV incidence over 2 years of 36%. A similar impact was achieved if treatment of syphilis was excluded from the intervention or confined to those in the infectious stages. In comparison with sustained syndromic treatment, single-round mass treatment had a greater short-term impact on HIV (36 versus 30% over 2 years), but a smaller long-term impact (24 versus 62% over 10 years). Mass treatment combined with improved treatment services led to a rapid and sustained fall in HIV incidence (57% over 2 years; 70% over 10 years).
Conclusions: In populations in which STD control can reduce HIV incidence, mass treatment may, in the short run, have an impact comparable to sustained syndromic treatment. Mass treatment combined with sustained syndromic treatment may be particularly effective.
From the aDepartment of Public Health, Erasmus University, Rotterdam, The Netherlands, the bAfrican Medical and Research Foundation, Mwanza, Tanzania, the cLondon School of Hygiene and Tropical Medicine, London, UK and the dEuropean Commission, Brussels, Belgium.
Sponsorship: The study was supported and financed by the Commission of the European Communities (contracts B7.6211/96/010 and B7.6211/97/017).
Correspondence to Eline L Korenromp, Centre for Decision Sciences in Tropical Disease Control (CDTDC), Department of Public Health, Faculty of Medicine & Health Sciences, Erasmus University Rotterdam, PO Box 1738, 3000 DR Rotterdam, The Netherlands. Tel: +31 10 408 7714 / 7985; fax: +31 10 408 9449 / 9455; e-mail: firstname.lastname@example.org
Received: 8 January 1999;
revised: 11 November 1999; accepted: 2 December 1999.