introduction to 2nd generation hiv surveillance
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Introduction to 2nd Generation HIV Surveillance. UNAIDS/WHO Working Group on Global HIV/AIDS and STI Surveillance. Public Health Surveillance of HIV. - PowerPoint PPT PresentationTRANSCRIPT
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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
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2
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3
3.5
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
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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.