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Introduction to 2nd Generation HIV Surveillance

UNAIDS/WHO Working Group on Global HIV/AIDS and STI Surveillance

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Public Health Surveillance of HIV

The collection, analysis and dissemination of epidemiological information of sufficient accuracy and completeness regarding the

distribution and spread of HIV infection to be relevant to the planning, implementation

and monitoring of HIV/AIDS prevention and control programmes.

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HIV/AIDS: Data Needs

What are the levels and trends in HIV infection? Who is getting infected? Who is at risk for or vulnerable to HIV infection? What is the impact of the epidemic? Is the response effective?

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Use of STI/HIV surveillance data

Situation analysis Strengthen commitment Resource mobilization Targeting interventions Planning and evaluation of intervention Programme assessment and evaluation

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Is HIV surveillance “special”? Unique epidemiology (multiple epidemics) Wide variation in prevalence No definite cure yet Very long asymptomatic (latency) period Severity of AIDS Severe personal and social implications of

identifying HIV-infected persons

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A global view of HIV infectionA global view of HIV infection 33 million adults living with HIV/AIDS as of end 199933 million adults living with HIV/AIDS as of end 1999

Adult prevalence rate

15.0% – 36.0% 5.0% – 15.0% 1.0% – 5.0% 0.5% – 1.0% 0.1% – 0.5% 0.0% – 0.1% not available

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Incidence Curves

0

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1

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2

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3

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4

4.5

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Years of Epidemic

Perc

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Tanzania Incidence

Uganda Incidence

Lagged Zimbabwe Incidence

Lagged Cambodia Incidence

Lagged Honduras Incidence

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UNAIDS/WHO Classification of epidemic states

LOW LEVEL: HIV prevalence has not consistently exceeded five percent in any

defined sub-population CONCENTRATED

HIV prevalence consistently over five percent in at least one defined sub-population but below one percent in pregnant women in urban areas.

GENERALISED HIV prevalence consistently over one percent in pregnant women

nation-wide

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LOW LEVEL Principle: Although HIV infection may have existed for

many years, it has never spread to significant levels in any sub-population.

Infection is largely confined to individuals with higher risk behaviour: e.g. sex workers, drug injectors, MSM. This suggests that networks of risk are rather diffuse (low levels of partner exchange or sharing of drug injecting equipment), or a very recent introduction of the virus.

Numerical proxy: HIV prevalence has not consistently exceeded five percent in any defined sub-population.

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CONCENTRATED Principle: HIV has spread rapidly in a defined sub-

population, but is not well-established in the general population.

This suggests active networks of risk within the sub-population. The future course of the epidemic is determined by the frequency and nature of links between highly infected sub-populations and the general population.

Numerical proxy: HIV prevalence consistently over five percent in at least one defined sub-population. HIV prevalence below one percent in pregnant women in urban areas

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GENERALISED Principle: In generalised epidemics, HIV is firmly

established in the general population. Although sub-populations at high risk may continue

to contribute disproportionately to the spread of HIV, sexual networking in the general population is sufficient to sustain an epidemic independent of sub-populations at higher risk of infection.

Numerical proxy: HIV prevalence consistently over one percent in pregnant women nation-wide.

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LESSONS LEARNED from HIV surveillance

Strengths Relatively simple and

cheap Increase awareness

and raise commitment

Generating response Target activities Monitor success

Weaknesses No risk behaviours Poor early warning Little use of other

sources of data “One size fits all” Not suitable for “slow” or

“mature” epidemics It is difficult to derive HIV

prevalence estimates

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2nd generation HIV surveillance It is not “new or different” but “improved” Builds on the lessons learnt in the first decade of surveillance for HIV Attempts to capture the diversity of the HIV epidemics in different

areas Considers the state of the epidemic

low-level concentrated generalised

Integrates biological surveillance (AIDS, HIV) with “RISK” surveillance (behaviours, STI)

Looks at new methodologies and improved ways for using HIV epidemiological data

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2nd generation HIV surveillance

AIDS reporting

HIV surveillance

STI surveillance

behavioural surveillance

Data management

HIV estimates and projections

Use of data for action

Data analysis

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0102030405060708090

“WINDOW”PERIOD

INFECTIONASYMPTOMATIC PERIOD HIV ILLNESS

or AIDS DEATH

“RISK”SURVEILLANCE

HIV INCIDENCESURVEILLANCE

HIV PREVALENCESURVEILLANCE

AIDS CASESURVEILLANCE

AIDSDEATHS

= VIRAL LOAD = HIV ANTIBODIES

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Courtesy of Dr. Thomas Rehle, Family Health International

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Data collection methods Biological surveillance

Sentinel sero surveillance in defined sub-populations Regular HIV screening of donated blood Eventual regular HIV screening of other sub-populations HIV screening of specimens taken in population surveys

Behavioural surveillance Repeat cross-sectional surveys in the general population Repeat cross-sectional surveys in defined sub-populations

Other sources of information HIV and AIDS case surveillance Death registration STD surveillance, TB surveillance, Hepatitis surveillance

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Key questions for low-level and concentrated epidemics: a summary Is there any risk behaviour that might lead to an HIV

epidemic? In which sub-populations is that behaviour concentrated? What is the size of those sub-populations? How much HIV is there in those sub-populations? Which behaviours expose people to HIV in those sub-

populations and how common are they? What are the links between sub-populations at risk and

the general population?

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Surveillance in low-level epidemics

Cross-sectional surveys of behaviour in sub-populations with risk behaviour

Surveillance of STDs and other biological markers of risk

HIV surveillance in sub-populations at risk HIV and AIDS case reporting Tracking of HIV in donated blood

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Surveillance in concentrated epidemics

HIV and STI/behavioural surveillance in sub-populations with risk behaviour

HIV and behavioural surveillance in bridging groups

Cross-sectional surveys of behaviour in the general population

HIV sentinel surveillance in the general population, urban areas

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Key questions for surveillance in a generalised epidemic

What are the trends in HIV infection? To what extent do trends in behaviour

explain trends in prevalence? Which behaviours have changed following

interventions and which continue to drive the epidemic?

What impact is the epidemic likely to have on individual, family and national needs?

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Surveillance in generalised epidemics

Sentinel HIV surveillance among pregnant women, urban and rural

Cross-sectional surveys of behaviour in the general population

Cross-sectional surveys of behaviour among young people

HIV and behavioural surveillance in sub-populations with high risk behaviour

Data on morbidity and mortality

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

Jun-

89

Dec

-89

Jun-

90

Dec

-90

Jun-

91

Dec

-91

Jun-

92

Dec

-92

Jun-

93

Dec

-93

Jun-

94

Dec

-94

Jun-

95

Dec

-95

Jun-

96

Jun-

97

Jun-

98

Jun-

99

HIV Prevalence Among Pregnant Women, Male Conscripts, and Donated Blood

Thailand 1989-1999%

Month/Year

Pregnant women

Donated blood

Source: Sentinel Serosurveillance, Division of Epidemiology, Ministry of Public Health.Remark: Switching from bi-annually (June and December) to annually in June since 1995 Conscript data in November of each year since 1995 were not shown here

Conscripts (age 21)

Clients Using Condoms andSTI Cases Reported - Thailand

0102030405060708090

100

1982

1983

1984

1985

1986

1987

1988

1989

1990

1991

1992

1993

1994

1995

1996

1997

Clients using condom

STI cases reported

STI cases reported ( thousands) % using condoms

100 90 80 70 60 50 40 30 20 10 0

Source: Sentinel Serosurveillance, Division of Epidemiology, Ministry of Public Health.