Introduction to 2nd Generation HIV Surveillance UNAIDS/WHO Working Group on Global HIV/AIDS and STI Surveillance
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.
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?
Use of STI/HIV surveillance data • Situation analysis • Strengthen commitment • Resource mobilization • Targeting interventions • Planning and evaluation of intervention • Programme assessment and evaluation
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
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 A global view of HIV infection33 million adults living with HIV/AIDS as of end 1999
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
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.
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
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.
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 LESSONS LEARNED from HIV surveillance
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
Data management Data analysis HIV estimates and projections Use of data for action 2nd generation HIV surveillance STI surveillance HIV surveillance behavioural surveillance AIDS reporting
HIV PREVALENCE SURVEILLANCE AIDS DEATHS “RISK” SURVEILLANCE HIV INCIDENCE SURVEILLANCE AIDS CASE SURVEILLANCE “WINDOW” PERIOD HIV ILLNESS or AIDS ASYMPTOMATIC PERIOD DEATH INFECTION = VIRAL LOAD = HIV ANTIBODIES
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
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?
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
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 generalpopulation, urban areas
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?
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
HIV Prevalence Among Pregnant Women, Male Conscripts, and Donated Blood Thailand 1989-1999 % 4.5 Conscripts (age 21) 4 3.5 3 2.5 Pregnant women 2 1.5 Donated blood 1 Month/Year 0.5 0 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 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
Clients Using Condoms andSTI Cases Reported - Thailand % using condoms STI cases reported ( thousands) 100 90 80 70 60 50 40 30 20 10 0 100 90 80 70 60 50 Clients using condom 40 30 STI cases reported 20 10 0 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 Source: Sentinel Serosurveillance, Division of Epidemiology, Ministry of Public Health.