Section 1: Core Epidemiologic Questions
Whether you are preparing an HIV/AIDS epidemiologic profile for prevention or care, you
should answer 3 essential epidemiologic questions:
- What are the
sociodemographic
characteristics of
the general
population in your
service area?
- What is the scope
of the HIV/AIDS
epidemic in your
service area?
- What are the
indicators of risk for
HIV infection and
AIDS in the population
covered by your
service area?
Examining groups at risk for HIV infection and answering these core questions will help you
understand the characteristics of the population in your service area, the distribution of HIV
disease, and how the epidemic may look in the future. The answers provide the basis for setting
priorities among populations and then identifying appropriate interventions and services.
Answering these core questions is the first step in developing your comprehensive HIV prevention and care plan. Answer the questions as completely as possible, basing your answers
on the needs, available data, and resources in your area.
The remainder of this chapter presents recommended analyses that will help you answer the
questions. First, however, it briefly describes the importance of changes in the epidemic and
HIV/AIDS surveillance data and their potential effect on epidemiologic profiles.
Changes in the Epidemic and Data That Affect Profiles
Describing the HIV/AIDS epidemic in the United States relies heavily on surveillance data
collected through the coordinated efforts of public health officials and private and public health
care professionals throughout the country. States and territories collect data locally and share it
with CDC. State, territory, and local health departments and CDC analyze and disseminate the
data in a variety of formats for use by public health, prevention and care planning, and health
communications and news organizations. The epidemiologic profile you prepare is part of the
local dissemination of data to provide an understanding of the HIV/AIDS epidemic and assist in
setting priorities for prevention and care in your service area.
Supplementing surveillance data with other sources of data will help provide a more
comprehensive and in-depth picture of the epidemic in your service area.
To provide a balanced and accurate description of the epidemic that incorporates the strengths
and limitations of the data sources, you need to be aware of the changing nature of HIV/AIDS
and surveillance data.
Keep the following points in mind as you develop your epidemiologic profile. Because of the
successful effects of treatment and the expansion of surveillance data to HIV infection, you may
see changes in the trends of the epidemic in your service area.
- The number of persons reported as living with AIDS does not include persons who were not
tested, persons who were tested anonymously, or infected persons in whom HIV infection
has not progressed to AIDS. CDC estimates that at the end of 2000, 850,000 to 950,000
adults and adolescents were living with HIV (not AIDS) and AIDS.1
- In 2000, about one fourth of infected persons had no diagnosis and
may continue to be unaware of their infection.1 Thus, they
are not benefiting from improved health and survival associated with
antiretroviral therapy. Of HIV-infected persons with a diagnosis, one
third may not be receiving care.1
- Of the persons whose diagnosis of HIV was made during 1994–2000 and who were reported
from the 25 states with HIV reporting since 1994, approximately one fourth of those with a
new HIV diagnosis received a diagnosis of AIDS at the same time (these persons represent
those who are tested late in the disease process).2 Increased HIV testing early in the course of HIV disease and programs to link infected persons to ongoing care and prevention services
are essential to reducing the number of new infections.
- To enable us to better monitor and characterize the epidemic, CDC and the Council of State
and Territorial Epidemiologists have recommended that national surveillance be expanded to
include both HIV infection and AIDS cases.3,4 Such an integrated national HIV/AIDS case
surveillance system will provide information about persons whose HIV infection has been
newly diagnosed, including those with evidence of recent infection, those with severe HIV
disease (AIDS), and those dying of HIV disease or AIDS.
- Integrated HIV/AIDS surveillance data on new HIV and AIDS diagnoses provide a minimum
estimate of persons known to be infected. HIV diagnosis data may not reflect trends in HIV
incidence (new infections) because the data are affected by when in the course of disease a
person seeks or is offered HIV testing. Data on new infections can reflect incidence when
incidence, testing patterns, and mortality from competitive causes are constant over an
extended time. In addition, these data do not represent total HIV prevalence because not all
HIV-infected persons have been tested. Furthermore, because diagnoses based on
anonymous tests are not reported to confidential name-based registries, these data may not
represent all persons who test positive for HIV infection.
- Currently, HIV surveillance data must be interpreted with data
from additional sources (e.g., behavioral surveillance) to provide a
more complete picture of the epidemic. Whether a trend in the number
of new HIV diagnoses is stable, increasing, or decreasing may
reflect current or historical patterns in HIV incidence, changes in
testing behaviors, or the maturity of the epidemic in the geographic
area.5
1 Fleming PL, Byers RH, Sweeney PA, Daniels D, Karon JM, Janssen RS. HIV prevalence in the United States,
2000. In: Program and abstracts of the 9th Conference on Retroviruses and Opportunistic Infections; February 24–
28, 2002; Seattle, Washington. Abstract 11.
2 CDC.
Diagnosis and reporting of HIV and AIDS in states with HIV/AIDS surveillance—United States, 1994–2000.
MMWR 2002;51:595–598.
3 CDC.
Guidelines for national human immunodeficiency virus case surveillance, including monitoring for human immunodeficiency virus infection and acquired immunodeficiency syndrome.
MMWR 1999;48(No. RR-13):1–31.
4 Council of State and Territorial Epidemiologists. CSTE position statement ID-4: national HIV surveillance―addition to the national public health surveillance system. Atlanta: Council of State and Territorial Epidemiologists; 1997.
5 CDC. HIV/AIDS Surveillance Update 2000;1(No. 1):1–48
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