Abbreviated Name:
Estimated number of new HIV infections
Indicator Name:
Estimated number of new HIV infections
Domain:
Health status / Morbidity
Related Terms:
Human Immunodeficiency Virus (HIV), acquired immunodeficiency syndrome (AIDS ).
Definition:
The estimated number of new HIV infections per 1000 uninfected population, by sex, age and key populations as defined as the number of new HIV infections per 1000 persons among the uninfected population.
Measurment Method:
Methods for monitoring incidence can vary depending on the epidemic setting and are typically categorized either as direct or indirect measures. Direct measurement at a population level is preferred but can often be difficult to obtain. As a result, most if not all countries rely on indirect measures or triangulate direct and indirect methods.
Strategies for directly measuring HIV incidence include longitudinal follow-up and repeat testing among individuals who do not have HIV infection and estimation using a laboratory test for recent HIV infection and clinical data in the population. Longitudinal monitoring is often costly and difficult to perform at a population level. Laboratory testing of individuals to determine the recency of infection also raises cost and complexity challenges since a nationally representative population-based survey is typically required to obtain estimates.
Indirect methods most frequently rely on estimates constructed from mathematical modelling tools, such as Spectrum or the AIDS Epidemic Model. These models may incorporate geographical and population-specific HIV surveys, surveillance, case reporting, mortality, programme and clinical data and, in some instances, assumptions about risk behaviour and HIV transmission. In some instances, countries may wish to triangulate these data with other sources of estimates of the number of people newly infected, including from serial population-based HIV prevalence estimates or estimates of HIV prevalence in young, recently exposed populations.
Note that case-based surveillance systems capturing newly reported people acquiring HIV infection should not be used as a direct source of estimating the number of people newly infected with HIV in the reporting year. Because of reporting delays and underdiagnosis, newly reported cases may not reflect the actual rate of people becoming newly infected. This information may be useful, however, for triangulation or validation purposes, especially when combined with tests for the recency of HIV infection.
Disaggregated data reported for the numerator should be used to monitor progress towards eliminating new child infections and reducing the number of new HIV infections among adolescent girls and young women to below 100 000 per year.
Strategies for directly measuring HIV incidence include longitudinal follow-up and repeat testing among individuals who do not have HIV infection and estimation using a laboratory test for recent HIV infection and clinical data in the population. Longitudinal monitoring is often costly and difficult to perform at a population level. Laboratory testing of individuals to determine the recency of infection also raises cost and complexity challenges since a nationally representative population-based survey is typically required to obtain estimates.
Indirect methods most frequently rely on estimates constructed from mathematical modelling tools, such as Spectrum or the AIDS Epidemic Model. These models may incorporate geographical and population-specific HIV surveys, surveillance, case reporting, mortality, programme and clinical data and, in some instances, assumptions about risk behaviour and HIV transmission. In some instances, countries may wish to triangulate these data with other sources of estimates of the number of people newly infected, including from serial population-based HIV prevalence estimates or estimates of HIV prevalence in young, recently exposed populations.
Note that case-based surveillance systems capturing newly reported people acquiring HIV infection should not be used as a direct source of estimating the number of people newly infected with HIV in the reporting year. Because of reporting delays and underdiagnosis, newly reported cases may not reflect the actual rate of people becoming newly infected. This information may be useful, however, for triangulation or validation purposes, especially when combined with tests for the recency of HIV infection.
Disaggregated data reported for the numerator should be used to monitor progress towards eliminating new child infections and reducing the number of new HIV infections among adolescent girls and young women to below 100 000 per year.
Numerator:
Number of new HIV infections by sex, age and key populations
Denominator
Total uninfected population by sex, age and key populations
Estimation method:
Modelling is often used to obtain an estimate of new infections. Prevalence data are the main input data.
Disaggregation:
• Gender (female, male)
• Age (0–14, 15–49, 50+ years)
• Cities and other administrative regions of epidemiologic importance
• Age (0–14, 15–49, 50+ years)
• Cities and other administrative regions of epidemiologic importance
Primary data sources:
Household or key population survey with HIV incidence-testing
Spectrum modelling
Spectrum modelling
Alternate data sources:
Other possible data sources: Regular surveillance system among key populations.
Measurment frequency:
Annually