Strategic Information: Surveillance

::Second Generation Surveillance
::HIV Surveillance
::STI Surveillance
::Behavioural Surveillance
::AIDS Case Surveillance

Second Generation Surveillance

Second generation surveillance systems include HIV and STI surveillance and monitor risk behaviours, using them to warn of or explain changes in levels of infection. As the diversity of HIV epidemics becomes more apparent, it also becomes evident that there is no “one-size-fits-all” surveillance system.

Efficient surveillance of a predominantly heterosexual epidemic in a country where one adult in six is infected will differ radically from surveillance in a country where HIV infection is growing rapidly in drug injectors but has yet to spread to the general population. In general, surveillance systems can be divided into three broad types directly related to the type of epidemic:

  • In generalized epidemics where HIV is over one percent in the general population, surveillance systems concentrate on monitoring HIV infection and risk behaviour in the general population.
  • In concentrated epidemics where HIV is over five percent in any sub-population at higher risk of infection (such as drug injectors, sex workers, men who have sex with men), surveillance systems monitor infection in those groups and pay particular attention to behavioural links between members of those groups and the general population. They might ask, for example, whether male sex workers have wives or girlfriends, or whether drug users finance their habit through sex work. In these situations, surveillance systems also monitor the general population for high-risk sexual behaviour that might lead to rapid spread of the virus if it were introduced.
  • In low-level epidemics where relatively little HIV is measured in any group, surveillance systems focus largely on high-risk behaviours, looking for changes in behaviour which may lead to a burst of infection. Such changes have recently been recorded in several Eastern European countries, for example, where a surge in injecting drug use was followed by very rapid growth in HIV infection.

Quality of HIV Sero-surveillance

The quality of HIV sero-surveillance systems in countries is becoming more and more central to the monitoring and evaluation efforts. One of the global goals set out in the UNGASS Declaration of Commitment aims:

"By 2005, 60% of countries have adequate surveillance of HIV/AIDS, sexually transmitted infections and related behaviours."

These systems are the basis for countries to understand better their epidemic, to track changes over time, and tailor improved responses. In addition these systems are the basis for estimates of HIV/AIDS prevalence and mortality produced by WHO and UNAIDS. These in turn are used in the calculation of disease attributable to HIV/AIDS.

A review in 2001 revealed that 28% of the countries had fully implemented HIV surveillance systems, 31% had some or most aspects, and 41% poorly functioning or non-existent (Walker N et al., Epidemiological analysis of the quality of HIV sero-surveillance in the world: how well do we track the epidemic? AIDS 2001, 15: 1545-1554).

The analysis encompasses the assessment of quality of HIV based on the frequency and timeliness of data collection, the appropriateness of populations under surveillance, the consistency of the sites/ locations and groups measured over time, and the coverage/ representativeness of the groups for the adult populations.

WHO and their partners are currently carrying out a more comprehensive review of the quality of such systems for HIV, STI and behavioural data which should be completed by mid-2003. For the assessment of behavioural quality, the criteria are based on the timeliness of data collection too, and in addition, on the geographical coverage, the accuracy of indicators and populations under surveillance, and the consistency of the data collected over time.

Finally, for the assessment of quality of STI the analysis will focus for pregnant women on the quality of Syphilis serological surveillance and the availability and quality of Syphilis sero-prevalence data, and for vulnerable populations on the availability and quality of surveillance data with routine case reporting, and prevalence assessment in risk population groups.

WHO/UNAIDS Second Generation Surveillance Project

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Publications in preparation

The overall goal and objective of the EC supported HIV/AIDS surveillance project are to develop and field test the second generation surveillance framework proposed by WHO/UNAIDS by improving the collection, analysis and interpretation of data on HIV/AIDS, sexual behaviour and STI in a more sustainable fashion. During this phase of the project such systems are developed and implemented in eight developing countries with different epidemic states from the Africa, Latin America and Asia regions. The project started in 1999 and focuses its country support on eight countries: Burkina Faso, Dominican Republic, Mexico, Mozambique, Myanmar, Nigeria, Tanzania, and Vietnam.

For more information see the 2002 Progress report.

HIV surveillance

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All countries affected by the HIV epidemic need information about their epidemic in order to combat its spread. Information about trends in the spread of HIV —whether and by how much the rates are increasing or decreasing and which populations are affected—can help countries monitor the epidemic and provide information to improve planning and evaluation of prevention activities.

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STI surveillance

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More WHO/UNAIDS documents on STI

STI surveillance aims to improve the quality and effectiveness of STI and HIV control programmes and should be a key component of second generation surveillance systems. The five components of STI surveillance that are necessary for effective control programmes are: case reporting, prevalence assessment and monitoring, assessment of STI syndrome etiologies, antimicrobial resistance monitoring and special studies.

STIs are a major public health problem. WHO, in collaboration with UNAIDS, has established a reference group to make estimates of the incidence and prevalence of the major STIs in 2003. Such estimates were made for the global and regional levels in 1995 and 1998 (Gerbase AC, Rowley JT, Mertens TE. Global epidemiology of sexually transmitted diseases. Lancet 1998;351(suppl III):2-4). In 2003, country specific estimates will be made wherever the data permit to do so.

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Behavioural Surveillance

Data derived from behavioural surveillance, serve as an early warning system, provide information to guide programme design, help evaluate programmes and explain changes in HIV prevalence.

Often, behavioural surveillance is designed to track trends in behavioural indicators and is based on repeated cross-sectional surveys in selected population groups over time. The populations selected differ according to the type and stage of the epidemic.

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AIDS Case Surveillance

This type of surveillance consists of reporting of AIDS cases on a yearly basis. As of 22 November 2002, a total of 2 822 111 AIDS cases had been officially reported to WHO. Although AIDS cases continue to be reported to WHO, there are limitations due to great variation in completeness of AIDS case reporting and due to variation in AIDS case definitions between regions of the world.

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New Publications

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2003 update

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Providing a framework for partnership and action

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Archive 2003

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26-29 January 2004
New strategies for HIV/AIDS surveillance in resource constrained countries
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