|WHO Recommended Surveillance Standards (WHO - OMS, 1999, 157 p.)|
RATIONALE FOR SURVEILLANCE
The surveillance of HIV infection is the best way to forecast the future impact of AIDS on national health resources. It may also allow counselling, follow-up and chemoprophylaxis when appropriate at an individual level.
RECOMMENDED CASE DEFINITION
There is no clinical description; the diagnosis is based on laboratory criteria.
Laboratory criteria for diagnosis
HIV positive serology (ELISA)
Confirmation by a second serological test is necessary only in settings where estimated HIV prevalence is known to be <10%.
Confirmation should be a second ELISA or simple/rapid assay based on a different antigen preparation and/or a different test principle.
Suspected: Not applicable.
Probable: Not applicable.
Confirmed: A laboratory-confirmed case.
Note: Except for unlinked anonymous testing, serological testing should only be done in combination with appropriate pre- and post-counselling services. Western Blot is used for individual confirmation rather than for general HIV surveys, in countries which have the appropriate resources.
RECOMMENDED TYPES OF SURVEILLANCE
In countries where HIV prevalence is low (e.g., £1% among pregnant women or other groups representative of the general population) and where infections are concentrated in a few high-risk sub-groups of the population, the current trend is to monitor the scope and course of the epidemic through HIV case reporting (HIV case surveillance). This approach is currently used mainly in developed countries, where a majority of those who are HIV positive have access to testing and are actually tested.
In areas of relatively high prevalence and in developing countries, the method of preference is unlinked anonymous testing in sentinel sites. In order to monitor time trends it is necessary to ensure continuity of the same sentinel surveillance sites over time, and to ensure that within sites the same sampling scheme is used over time (periodical and standardized).
For countries with low prevalence, the sentinel sites should focus on testing of high-risk groups (patients seeking treatment for sexually transmitted diseases, users of intravenous drug use, or commercial sex workers seeking health care treatment etc.).
For countries with higher prevalence, monitoring of high risk groups should continue, and surveillance of general population groups such as pregnant women attending antenatal clinics should be carried out.
Routine yearly reporting of HIV prevalence data from each sentinel site to intermediate and to central level. Some countries report case-based data. Other sources of data:
· Antenatal clinics
· STD clinics
· Blood banks
· Army (data from army recruits)
· Special surveys
· Mortality reports
RECOMMENDED MINIMUM DATA ELEMENTS
Case-based data for reporting
· Age, sex, location, risk factors
Aggregated data for reporting
· On a yearly basis: number of cases tested by age, sex, patient group, sentinel site (where appropriate)
RECOMMENDED DATA ANALYSES, PRESENTATION. REPORTS
· Analysis of prevalence by age and sex and geographic area, rural/urban locations and population subgroups, risk factors
· Analysis of trends in prevalence over time, by age and sex and geographic area, rural/urban location and population subgroup
· Graphs and tables: prevalence and confidence intervals, by year, age and sex, by sentinel site, population subgroup, geographic area, rural/urban location
· Maps: prevalence levels at each sentinel site
PRINCIPAL USES OF DATA FOR DECISION-MAKING
· Assess the current magnitude and current trends of the HIV/AIDS epidemic
· Project the number of AIDS cases over the next 5 years
· Identify high risk population sub-groups and/or geographic areas for intervention
· Evaluate the impact of specific interventions
· Assess impact on health services, plan health and social service activities for people with HIV/AIDS
· Increase public and political awareness of the disease
See Regional Communicable Disease contacts on section "Communicable disease contacts in Regional Offices".
Headquarters: WHO, 20 Avenue Appia, CH-1211 Geneva 27, Switzerland
UNAIDS/WHO Working Group on Global HIV/AIDS and STD Surveillance
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Tel: (41 22) 791 2403/2526
Fax: (41 22) 791 4198