Most-at-risk Populations: Reduction in HIV Prevalence

Export Indicator

Percentage of most-at-risk populations who are HIV-infected
What it measures

To assess progress on reducing HIV prevalence among most-at-risk populations
Most-at-risk populations typically have the highest HIV prevalence in countries with either concentrated
or generalized epidemics. In many cases, prevalence among these populations can be more than double the prevalence among the general population. Reducing prevalence among most-at-risk populations is a critical measure of a national-level response to HIV. This indicator should be calculated separately for each population that is considered most-at-risk in a given country: sex workers, injecting drug users, men who have sex with men.

Note: countries with generalized epidemics may also have a concentrated subepidemic among one or
more most-at-risk population. If so, it would be valuable for them to calculate and report on this indicator
for those populations.


Number of members of most-at-risk population who test positive for HIV


Number of members of most-at-risk population tested for HIV


Numerator / Denominator

Method of measurement

This indicator is calculated using data from HIV tests conducted among members of most-at-risk population groups in the primary sentinel site or sites.

The sentinel surveillance sites used for the calculation of this indicator should remain constant to allow for the tracking of changes over time.

In theory, assessing progress in reducing the occurrence of new infections is best done through monitoring changes in incidence over time. However, in practice, prevalence data rather than incidence data are available. In analysing prevalence data of most-at-risk-populations for the assessment of prevention programme impact, it is desirable not to restrict analysis to young people but to report on those persons who are newly initiated to behaviours that put them at risk for infection (e.g. by restricting the analysis to people who have initiated injecting drug use within the last year or participated in sex work for less than one year, etc.). This type of restricted analysis will also have the advantage of not being affected by the effect of antiretroviral therapy in increasing survival and thereby increasing prevalence. In the Country Progress Report, it is imperative to indicate whether this type of analysis is used to allow for meaningful global analysis.


Measurement frequency



Condom type: N/A

Education: N/A

Gender: Male, Female

Geographic location: N/A

HIV status: N/A

Pregnancy status: N/A

Sector: N/A

Service Type: N/A

Target: N/A

Time period: N/A

Type of orphan: N/A

Vulnerability status: N/A

Explanation of the numerator
Explanation of the denominator
Strengths and weaknesses

 Due to diffi culties in accessing most-at-risk populations, biases in serosurveillance data are likely to be far more significant than in data from a more general population, such as women attending antenatal clinics. If there are concerns about the data, these concerns should be reflected in the interpretation.

An understanding of how the sampled population(s) relate to any larger population(s) sharing similar risk behaviours is critical to the interpretation of this indicator. The period during which people belong to a most-at-risk population is more closely associated with the risk of acquiring HIV than age. Therefore, it is desirable not to restrict analysis to young people but to report on other age groups as well.
Trends in HIV prevalence among most-at-risk populations in the capital city will provide a useful indication of HIV-prevention programme performance in that city. However, it will not be representative of the situation in the country as a whole.

The addition of new sentinel sites will increase the samples representativeness and will therefore give a
more robust point estimate of HIV prevalence. However, the addition of new sentinel sites reduces the
comparability of values. As such it is important to exclude new sites from the calculation of this indicator
when undertaking trend analyses.

Further information

Revised guidelines on HIV surveillance on most-at-risk populations are currently being prepared by the
WHO/UNAIDS Global Working Group on STI/HIV Surveillance. For further information please refer