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:

1. What are the sociodemographic characteristics of the general population in your service area?
2. What is the scope of the HIV/AIDS epidemic in your service area?
3. 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

Go to Chapter 3, Section 1, Question 1