HIV prevalence in sub-populations with high-risk behaviour
In countries with concentrated epidemics, tracking of HIV infection among pregnant women may be a waste of resources. In any case, the bulk of interventions in concentrated epidemics are often focused on the behaviours or groups which are contributing most to the expansion of the epidemic. In a concentrated epidemic, these generally include one or more of the following: injecting drug users, men who have sex with other men, sex workers and frequent clients of sex workers. The design of a second generation surveillance system should take into account the epidemic state. In countries with low-grade or concentrated epidemics, surveillance for the HIV virus as well as behavioural surveillance should focus on those groups where both infection and interventions are concentrated. Changes in HIV prevalence in these groups should reflect the success or failure of prevention attempts.
Number of members of the at-risk sub-population testing positives for HIV at sub-population sentinel sites
Total number of members of the at-risk sub-population tested for HIV
Tracking HIV in sub-populations can be logistically and ethically difficult, especially if the groups are marginalised or their activities are illegal. Sampling and estimation of total population sizes are key issues. An understanding of how the sampled population relates to any larger population sharing similar risk behaviours is critical to the interpretation of the indicator. For some groups, population-based sampling strategies will be necessary. In other cases, sentinel sites are available. Sentinel sites for these populations tend to be linked to the provision of health services, for example, a mens health clinic in an area with a high concentration of gay sex bars, or a drug rehabilitation centre. The indicator is the number of members of the at-risk sub-population testing positive for HIV at sub-population sentinel sites, divided by the total number of members of the at-risk subpopulation tested for HIV.
Geographic location: N/A
Pregnancy status: N/A
Target: Sex workers, Clients of sex workers, Injecting drug users, Men who have sex with men
Time period: N/A
Type of orphan: N/A
Vulnerability status: N/A
Because of the difficulties in access to sub-populations, the biases in sub-population serosurveillance data are likely to be far greater (and much less predictable) than in data from a more generalised population such as women at antenatal clinics. Where sentinel sites provide health services to the sub-population in question, for example, the use of the facility may be associated with problems that are themselves related to HIV infection. It is especially difficult to minimise biases associated with age, since the age of participation in especially high-risk behaviours may vary widely. It is not, therefore, desirable simply to restrict the analysis to young people as it is in ANC sentinel sites. Despite these difficulties, it is essential to track HIV infection in those with higher risk behaviours in concentrated epidemics. The information will not be perfect, but some measure of progress or lack thereof will be essential to maintain support for prevention programmes in critical sub-populations.