Guidelines for second generation HIV surveillance - World Health ...

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Assessing the current level of HIV prevalence in a generalized epidemic A geographical area classified as having a generalized epidemic should have sufficient data to indicate that HIV has penetrated sexual networks outside of the traditional key populations at higher risk: sex workers, men who have sex with men and people who inject drugs. In these settings, combining the level of HIV prevalence and size of the different risk subpopulations may help you to determine the relative contribution of different subpopulations to the epidemic. In some generalized epidemic settings, it might be difficult to allocate resources towards focusing surveillance and prevention interventions only on populations at higher risk for HIV instead of focusing efforts on the general population or specific age groups within the population. However, programme interventions among key populations at increased risk are still recommended and can indeed make a significant impact on a generalized epidemic. Tracking the level of HIV prevalence among antenatal clinic attendees In generalized epidemics, monitoring the level of HIV prevalence among the general population is as important as measuring the spread. HIV sentinel surveillance among women attending ANC is an easy way to reach a sample of the general population (10). ANC attendees are a proxy for the general population. However, women attending ANC tend to be young (depending on the fertility patterns in the country) and are by definition not using condoms. Thus, HIV prevalence among ANC attendees may be different from HIV prevalence among the adult population. HIV prevalence among ANC clients will change if fertility levels change in the country. However, comparing HIV prevalence among ANC attendees by geographical region is useful for identifying the hotspots in a country as well as getting a sense of trends over time. ANC prevalence together with programmatic data can be used to estimate national HIV prevalence using different tools (11,12). More information about methods and tools is available at http://www.unaids.org/en/ dataanalysis/epidemiology/. As services for PMTCT are scaled up and coverage reaches over 90%, countries are increasingly considering substituting data from clinics which provide testing services for mother-to-child transmission (MTCT) for data from sentinel surveillance among ANC attendees. Several research studies are under way to see how the transition from the use of ANC data to the use of MTCT data can be done. Further guidance is being developed based on the experience of some countries. The role of national population-based surveys in tracking the level of HIV prevalence National population-based surveys can provide the geographical distribution of risk and prevalence level by different populations. These surveys are very useful because they combine HIV prevalence information with many other indicators for each individual respondent. This allows for extensive analysis of factors that are associated with HIV infection. As shown in Figure 2.2, stratification by different regions can provide insight into the hotspots of the HIV epidemic. This kind of survey is useful only in countries with national HIV prevalence levels above 2%. Due to the cost and complexity of such surveys, they should be implemented only every three to five years, depending on the level of the HIV epidemic and the cost involved. Technical guidance notes can be found at http://www. unaids.org/en/media/unaids/contentassets/documents/epidemiology/20101207_HIVtesting_in_surveys_ WG_en.pdf. There are a few potential biases in these surveys. First, it is important to check refusal rates. People who know their status or feel they are likely to be infected might refuse to be tested, which could potentially bias the results. Second, national population surveys focus on individuals living in households, and therefore exclude people who are in hospitals or who live on the streets. However, this is unlikely to bias the results unless the population not living in households represents more than 5% of the population. 18
Figure 2.2. Stratification by region (national population surveys in South Africa, Human Sciences Research Council [HSRC] 2002, 2005, 2008) Percent 40.0 35.0 30.0 25.0 20.0 15.0 10.0 5.0 12.4% 11.3% 15.8% 28.4% 15.6% Evaluating a National Surveillance System 0.0 Tribal areas Farms Urban formal Urban informal Total Locality type 2.3. Create a national picture: map epidemiological zones Compiling available information for each geographical unit allows the identification of areas where the epidemic appears to be well established. Areas where key populations at higher risk are present and are of substantial size also need to be identified. Finally, additional information must be used on behavioural risk and HIV prevalence among populations with high-risk behaviours to look for broad patterns that indicate the potential for new infections. Continue to refine your map. Look for groupings of geographical units that share epidemic patterns. Put them into epidemiological zones linked by: • a shared higher-risk population, such as transport corridors along which key populations with high-risk behaviours circulate; • common higher-risk contexts, such as agricultural or industrial belts that attract migrant labour; • sociocultural practices that can be risk factors for HIV transmission such as traditional sex work. An epidemiological zone may be a whole country or may coincide with a sociopolitical unit, for example, a state, province or district. Alternatively, a zone may span several adjoining administrative units, for example, a coastal belt of districts, a region of northern provinces or a subarea within an administrative area, for example, a large city within a province. An epidemiological zone forms a corridor of transmission, where key populations with high-risk behaviours migrate from one area and transmit disease or seed epidemics among populations in another area. Some examples from countries can be seen below. An example from Indonesia: mapping the epidemic Indonesia is a large country with a diverse and mobile population, spread across many islands. Evidence from a range of behavioural and biological surveys and other surveillance data suggests that the epidemic in Indonesia is a mix of low-level and concentrated local epidemics among sex workers and persons who inject drugs (Figure 2.3). 19
Page 1 and 2: UNAIDS/WHO Working Group on Global
Page 3 and 4: UNAIDS/WHO Working Group on Global
Page 5 and 6: Contents Acknowledgements 1. Introd
Page 7 and 8: 1. Introduction 1.1. What is second
Page 9 and 10: 1.4. What this update includes This
Page 11 and 12: • Data from interventions or prog
Page 13 and 14: Epidemic categories Low-level epide
Page 15 and 16: If data from proxy groups have been
Page 17 and 18: 2.2.2. Step 2: Estimate the size of
Page 19 and 20: Table 2.3. Summary of methods for e
Page 21: In generalized epidemics, distingui
Page 25 and 26: Figure 2.4. HIV prevalence among AN
Page 27 and 28: 3. Design a comprehensive surveilla
Page 29 and 30: Tips for developing a national surv
Page 31 and 32: Low-level epidemic: brief explanato
Page 33 and 34: Surveillance activities for general
Page 35 and 36: Track key events where the burden o
Page 37 and 38: 3.1.4. Understand mortality trends
Page 39 and 40: • Prepare annual reports of the e
Page 41 and 42: As much as possible, this type of e
Page 43 and 44: Figure 4.2. Using HIV prevalence tr
Page 45 and 46: • Individuals may migrate to urba
Page 47 and 48: Probability surveys are the most ri
Page 49 and 50: Trends among young people or recent
Page 51 and 52: Figure 4.6. Asian Epidemic Model pr
Page 53 and 54: More precise risk behaviour data th
Page 55 and 56: Using data to plan programmes in In
Page 57 and 58: Figure 4.9. Results from Modes of T
Page 59 and 60: How to deal with data aggregation i
Page 61 and 62: Figure A.3. HIV sentinel surveillan
Page 63 and 64: Initiating second generation HIV su
Page 65 and 66: Networks (social, sexual) Outcome P
Page 67 and 68: 17. Patel SV et al. Filling a gap:
Page 69 and 70: Notes .............................
Page 72:
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