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

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AIDS case reporting

HIV surveillance

STI surveillance

Behaviouralsurveillance

Data management

Data analysis and synthesis

HIV estimates and projections

Use of data for action

*Monitoring and evaluation is on-going

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.

2. Which of the following is one of the epidemiologic principles that guide HIV surveillance?

a. HIV infections are not uniformly distributed in a population.

b. There are a limited number of ways that HIV can be transmitted.

c. HIV infection enters different areas and populations at different times, and spreads at different rates.

d. all of the above

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Answers to Warm Up Questions, Cont.

3. 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.

4. 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.

5. 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.

6. Which type of surveillance better describes the clinical disease burden of the HIV epidemic?

a. AIDS case surveillance

b. HIV sero-surveillance

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Answers to Warm Up Questions, Cont.

7. 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.

a. over-represent

b. under-represent

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Answers to Warm Up Questions, Cont.

8. Which of the following is an objective of HIV surveillance?

a. identifying sub-groups at greater or lesser risk for infection

b. monitoring trends in the prevalence of infection over time

c. assessing risk factors of HIV transmission

d. all of the above

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Answers to Warm Up Questions, Cont.

9. 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.

10. 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.

We’ll 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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