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 serosurveillance
• identify the strengths and weaknesses of each
• describe how the two are complementary

identify the main objectives of HIV serosurveillance

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
High Risk Populations
Antenatal clinics
Military conscription
health intake
centres





STI clinics
Drug treatment
centres
Jails
Tuberculosis (TB)
clinics
Hospital wards
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HIV Sero-Surveillance
Objectives

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-Surveillance
Objectives, 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 populationbased 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.
Prevalence
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



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 of
HIV 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
AIDS case
reporting
HIV
surveillance
STI
surveillance
Behavioural
surveillance
Data management
Data analysis and synthesis
HIV estimates and projections
Use of data for action
*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 serosurveillance 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 seroprevalence 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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