Unit 1: Objectives and Approaches to HIV Surveillance

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Unit 1 Objectives and Approaches to HIV
Surveillance
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Warm Up Questions Instructions

• Take five minutes now to try the Unit 1 warm up
  questions in your manual.
• Please do not compare answers with other
  participants.
• Your answers will not be collected or graded.
• We will review your answers at the end of the
  unit.

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What You Will Learn

• By the end of this unit you should be able to
• define the following terms
• HIV surveillance
• second-generation HIV surveillance
• HIV sero-surveillance
• HIV sentinel surveillance
• describe how epidemiologic principles, and also
  the state of the epidemic in a given location,
  guide HIV sero-surveillance

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What You Will Learn, Cont.

• By the end of this unit you should be able to
• compare AIDS case surveillance and HIV
  sero-surveillance
• identify the strengths and weaknesses of each
• describe how the two are complementary
• identify the main objectives of HIV
  sero-surveillance
• describe the three main approaches to conducting
  HIV sero-surveillance

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What You Will Learn, Cont.

• By the end of this unit you should be able to
• describe HIV incidence surveillance
• identify other sources of HIV testing data that
  can be used for HIV surveillance, in the context
  of a second-generation HIV surveillance system

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Overview of HIV Surveillance

• HIV surveillance is the systematic and regular
  collection of information on the occurrence,
  distribution and trends in HIV infection and
  factors associated with its transmission.
• It monitors the risk of infection among specific
  populations
• It is done on an on-going basis for the purpose
  of public health action

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Overview of HIV Surveillance, Cont.

• There are two general approaches to HIV
  surveillance
• HIV case reporting
• HIV sero-surveillance
• Surveillance activities can either be active or
  passive.

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HIV Sero-Surveillance

• The core HIV surveillance activity in the African
  region is HIV sero-surveillance.
• HIV sero-surveillance is when you determine HIV
  prevalence by testing blood for HIV antibodies.
• Sero-prevalence means prevalence estimates
  obtained through sero-surveillance
• Surveys that collect blood for HIV or other tests
  (for example, syphilis) are called sero-surveys.

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HIV Sero-Surveillance, Cont.

• HIV sero-surveillance data focus primarily on
  three factors
• Person
• Place
• Time

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Epidemiologic Principles Underlying HIV
Sero-Surveillance

• HIV infections are not uniformly distributed in a
  population.
• There are a limited number of modes of HIV
  transmission
• HIV infection enters into different geographic
  areas and populations at different times, and
  spreads at different rates.

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HIV Sentinel Surveillance

• HIV sentinel surveillance is the main activity of
  HIV sero-surveillance, and includes
• Measuring the sero-prevalence of HIV infection in
  selected populations who are regularly seen at
  sentinel sites
• Collecting demographic characteristics and some
  data on high-risk behaviours

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Sentinel Sites Represent the General Population
or High-Risk Populations

• General Population
• Antenatal clinics
• Military conscription health intake centres

• High Risk Populations
• STI clinics
• Drug treatment centres
• Jails
• Tuberculosis (TB) clinics
• Hospital wards

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HIV Sero-SurveillanceObjectives

• assess the prevalence of HIV infection in
  population sub-groups
• monitor trends in the prevalence of HIV infection
  over time
• identify behaviours and risk factors for HIV
  transmission

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HIV Sero-SurveillanceObjectives, Cont.

• provide data to assist with public health
  decision-making
• educate the public on HIV
• guide scientific research
• make estimates and projections

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HIV Sero-Surveillance Approaches

• Clinic-based sero-surveys are cross-sectional
  surveys of persons seen at selected clinics or
  sites
• Community-based sero-surveys may be needed to
  reach specific difficult-to-reach populations who
  are not included in clinic-based sentinel sites.
• Population-based sero-surveys are designed to
  measure HIV prevalence in the general population
  directly.

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Sero-Surveillance Recommendations for
Sub-Saharan Africa

• Conduct HIV sentinel surveillance at ANCs.
• Consider periodic community and population-based
  sero-surveys, and HIV sentinel surveillance at
  other sites.

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HIV Incidence and Prevalence

• Prevalence measures the number of people with a
  given illness at a given time
• Incidence refers to the number of new cases in a
  given period of time

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HIV Incidence and Prevalence, Cont.

• Incidence
• provides a measure of the speed of spread of HIV
  in a population
• indicates where HIV prevention is needed
• influenced by levels of infection and risky
  behaviours

• Prevalence
• a measure of the level of infection in a
  population
• provides a measure of current and future need for
  care
• influenced by both the rate of new infections
  (incidence) and the rate at which infected people
  leave the population

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Measuring HIV Incidence

• Cohort studies
• Laboratory-based methods
• Repeat testers
• Mathematical modelling
• HIV prevalence in young age groups

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Other Sources ofHIV Prevalence Data

• Voluntary counselling and testing (VCT)
  programmes
• Routine HIV testing
• Blood transfusion safety checks
• Scientific research
• Screening of persons entering the military,
  seeking employment, or seeking other benefits

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Second-Generation HIV Surveillance

• Second generation surveillance is a group of
  goals and principles for tracking the epidemic,
  including
• a focus on trends of the epidemic over time
• a better understanding of the behaviours that
  drive the epidemic
• emphasis on the sub-populations at highest risk
  for infection
• better use of existing data
• flexibility to the states of the epidemic

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Possible Sources of Data in Second Generation
Surveillance

• data collected from sero-surveys
• data from behavioural surveys
• AIDS case reporting
• death registries
• STI surveillance
• TB surveillance

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Figure 1.1, Primary Components of
Second-Generation HIV Surveillance
Monitoring and evaluation is on-going
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States of the Epidemic

• Low-Level HIV prevalence has not consistently
  exceeded 5 in any defined sub-population and
  remains below 1 in pregnant women in urban
  areas.
• Concentrated HIV prevalence is consistently over
  5 in at least one defined sub-population but
  below 1 in pregnant women in urban areas
• Generalized HIV prevalence is consistently over
  1 in pregnant women.

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AIDS Case Surveillance

• AIDS case surveillance and HIV sero-surveillance
  are complementary
• AIDS case surveillance describes the clinical
  disease burden caused by the HIV epidemic
• There are several drawbacks to AIDS case
  reporting, due to the long latent period and,
  frequently, resource constraints.

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Integrated Disease Surveillance

• WHO Regional Office for Africa (AFRO) recommends
  improving AIDS case reporting in the context of
  Integrated Disease Surveillance (IDS).
• IDS is a system whereby all priority communicable
  diseases are reported together using the same
  form.

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Comparing AIDS Case Surveillance HIV
Sero-Surveillance
AIDS Case Surveillance HIV Sero-Surveillance
usually passively reported by care providers at healthcare facilities usually actively implemented by public health surveillance departments
under-reporting by providers may be severe under-reporting not an issue
measures morbidity or clinical disease burden usually collects no information on morbidity
AIDS has a long latent period before clinically apparent symptoms appear HIV may be detected very early in the course of infection
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Comparing AIDS Case Surveillance HIV
Sero-Surveillance, Cont.
AIDS Case Surveillance HIV Sero-Surveillance
low specificity of case definition high specificity of case definition
does not accurately indicate prevalence of HIV infection in population groups measures levels and trends in HIV prevalence in population groups
does not measure incidence of HIV infection does not measure incidence of HIV infection, although sero-prevalence in younger age groups may approximate recent incidence
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Warm Up Review

• Take a few minutes now to look back at your
  answers to the warm up questions at the beginning
  of the unit.
• Make any changes you want to.
• We will discuss the questions and answers in a
  few minutes.

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Answers to Warm Up Questions

1. HIV sero-surveillance refers to the component of
   second-generation HIV surveillance that measures
   HIV prevalence.

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Answers to Warm Up Questions, Cont.

• Which of the following is one of the
  epidemiologic principles that guide HIV
  surveillance?
• HIV infections are not uniformly distributed in a
  population.
• There are a limited number of ways that HIV can
  be transmitted.
• HIV infection enters different areas and
  populations at different times, and spreads at
  different rates.
• all of the above

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Answers to Warm Up Questions, Cont.

1. Because, ideally, blood donation is voluntary and
   measures to select donors at lowest risk of
   infection are in place, HIV prevalence data from
   blood banks are likely to under -estimate true
   prevalence in a population.

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Answers to Warm Up Questions, Cont.

1. True or false? In low level epidemics, HIV
   surveillance should primarily focus on measuring
   HIV prevalence in antenatal clinics. False

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Answers to Warm Up Questions, Cont.

• True or false? Second-generation HIV surveillance
  is a single method of conducting HIV
  surveillance. False

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Answers to Warm Up Questions, Cont.

• Which type of surveillance better describes the
  clinical disease burden of the HIV epidemic?
• AIDS case surveillance
• HIV sero-surveillance

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Answers to Warm Up Questions, Cont.

• Because of the long latent period from HIV
  infection to the onset of AIDS, AIDS case
  surveillance may ________ the magnitude of the
  epidemic early on, when the HIV epidemic is
  expanding.
• over-represent
• under-represent

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Answers to Warm Up Questions, Cont.

• Which of the following is an objective of HIV
  surveillance?
• identifying sub-groups at greater or lesser risk
  for infection
• monitoring trends in the prevalence of infection
  over time
• assessing risk factors of HIV transmission
• all of the above

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Answers to Warm Up Questions, Cont.

• True or false? Sentinel surveys are harder to do
  than population-based surveys. They give more
  accurate picture of the over-all HIV prevalence
  in a population. False.

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Answers to Warm Up Questions, Cont.

1. Selection bias is especially a concern for
   sentinel surveys, since people who choose to
   attend a particular facility may be different
   from those who do not use those sites.

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Small Group Discussion Instructions

• Get into small groups to discuss these questions.
  
• Choose a speaker for your group who will report
  back to the class.
• Take 15 minutes for this exercise.

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Small Group Reports

• Select one member from your group to present your
  answers.
• Discuss with the rest of the class.

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Case Study Instructions

• Try this case study individually.
• Well discuss the answers in class.

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Case Study Review

• Follow along as we go over the case study in
  class.
• Discuss your answers with the rest of the class.

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Questions, Process Check

• Do you have any questions on the information we
  just covered?
• Are you happy with how we worked on Unit 1?
• Do you want to try something different that will
  help the group?

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