Table 1. Epidemiologic parameters for control of STIs including HIV.
| Focus | Methods | Notes | |||
|---|---|---|---|---|---|
| Who? | High coverage of “core” populations of sex workers and men who have sex with men is the first priority. Drug users, also often at high risk through sexual transmission, should also be targeted. | Targeted interventions linked to outreach and clinical services. Several countries have committed to scaling-up targeted interventions to reach saturation coverage of these populations.39,40 | Targeting is highly efficient. Population-level impact is feasible with interventions directed to core populations who generally comprise less than 5% of the sexually active population. | ||
| Male bridge populations. Efforts should also be made to reach actual or likely clients of sex workers and other bridge populations who disseminate STIs from core networks to the general population. | STI clinic patients are men with recent exposure. Workplace interventions particularly in settings of migrant labour or mobility. Outreach, peer education and STI services in red light districts where transmission potential is high.40 | Bridge populations may account for 20% or more of the sexually active male population. Interventions likely to reach men at high probability of having STIs and/or acute HIV infection; many report recent sex worker contact. | |||
| STI patients and people living with HIV. A high proportion of STI clinic patients may have acute HIV infection | Provider initiated testing and counselling, STI screening, treatment and counselling for people living with HIV under care.16,41,42 | Strengthening STI services offers opportunities to treat STIs and offer risk reduction counselling and HIV testing. | |||
| What? | Curable ulcerative STIs. Control of curable genital ulcers is highly feasible. Control of these infections correlates well with stabilization of HIV.43–45 | Effective antibiotic treatment of chancroid and syphilis results in rapid cure. Combined with targeted prevention efforts, control or elimination is feasible. | Data and modelling have established that ulcerative STIs are the most important STI cofactors for HIV transmission.44 | ||
| Viral ulcerative STIs. HSV-2 being an incurable viral infection requires different control strategies. | Studies have demonstrated the feasibility of suppressing HSV-2 and reducing HSV-2 and HIV concentrations in genital secretions.46,47 | Ongoing research is exploring optimal regimens for HIV prevention. | |||
| Curable non-ulcerative STIs. Non-ulcerative STIs are prevalent and increase HIV transmission 2–4 times. | Effective antibiotic treatment of gonorrhoea or chlamydial infection reduces HIV viral load to normal levels.48 | Reductions in gonorrhoea and chlamydial infection have been reported in high and lower risk populations. | |||
| Where? | Effective targeting requires a 2-stage process: (i) identifying epidemiologic “hot-spots” where risk is present and/or transmission is believed to be taking place; and (ii) mapping of populations in those areas. | STI surveillance helps identify “hot-spots” in the first stage of mapping. STI case reports from sentinel STI clinics can be used to monitor trends of new male STIs at district levels. | Demonstrated in Thailand and Sri Lanka. Builds on historical experience with contact tracing and STI outbreak control in developed countries.49,50 | ||
| When? | STI control is most effective in preventing HIV transmission: (i) when STIs, particularly ulcers are poorly controlled; and (ii) early in HIV epidemics. | STI surveillance. STI case reports and STI prevalence surveys among high-risk populations can be used to assess impact and monitor trends. | Modelling has shown the potential contribution of STI control to HIV prevention at different phases of STI and HIV epidemics. | ||
HSV-2, herpes simplex virus type 2; STI, sexually transmitted infection.