Below are the answers to some frequently asked questions about AIDS surveillance data.

Who is counted as an AIDS case?
In order to be classified as an AIDS case, a person must be diagnosed with one or more of the "AIDS indicator" diseases or be HIV-infected with a CD4 T-lymphocyte count of less than 200 cells/ml. Only people with AIDS as defined by the Centers for Disease Control are reportable in Massachusetts. As of January 1, 1999, HIV infection without AIDS is a reportable condition in this state (although HIV infection not reported by name). Consequently, the number of people who meet the AIDS case definition should not be used as the sole indicator of the impact of HIV infection, since it provides a "lagging indicator" of the patterns of HIV transmission. Because the latency period between infection and development of disease is 10 years or longer, AIDS cases occurring now are indicative of HIV infections acquired 10 years ago.

What is the difference between the number of cases reported in a year and the number of cases diagnosed?
Every year, the AIDS Surveillance Program receives case reports from health care providers - the number of case reports received in a year constitutes the "reported" cases. Once the year is over, the number of cases reported for that year does not increase. On the other hand, every year a certain number of people are diagnosed with AIDS - these are the diagnosed, or incident, cases for the year. Many cases are reported several months after they are diagnosed; consequently, the number of cases diagnosed in any given year will increase even after the year is over. This means that the most recent year's diagnosed cases will not be complete until reporting is complete. Approximately 65-70% of cases are reported within 6 months of diagnosis.

When the number of AIDS cases is broken down by year by the AIDS Surveillance Program, it is almost always broken down in terms of diagnosed cases per year (unless a specific request is made for the number of reported cases), since this distribution better reflects occurrence of AIDS in patients over time.

Who is included when considering the number of cases in the state or in a particular city or county?
People are included in the AIDS database if they are residents of Massachusetts at the time of their diagnosis. This means that people initially diagnosed in a different state are not reported in Massachusetts, even if they live here now (Note: there are 356 out-of-state cases from early in the epidemic). People are counted as cases in the city in which they were living when initially diagnosed, even though they may currently be living in a different city.

A certain number of AIDS cases are reported each year with a prison listed as the residence at time of diagnosis. Routine reports compiled by the AIDS Surveillance Program on a monthly and quarterly basis (the monthly city/town list, the monthly and quarterly county reports, the quarterly Community Health Network Area report) do not include persons diagnosed in prisons in these geographic areas. Depending on the purpose of specific data requests, prisoners may or may not be included - whether they are included or not will be made clear.

Why can't the AIDS Surveillance Program provide numbers of AIDS cases for certain cities?
The confidentiality policy of the Bureau of Communicable Diseases does not allow release of information if it can be used to identify an individual. Therefore, if fewer than 5 residents in a city or town have been reported as AIDS cases, the AIDS Surveillance Program will not release this number. This policy is also used when reporting numbers of AIDS cases in demographic categories, such as sex and race.

What people are included in the race/ethnicity category called "Black"?
Race, ethnicity and country of birth information is collected for all reported AIDS cases. For purposes of examining demographics of reported cases, people are grouped into the general categories "White", "Black (non-Hispanic)", "Hispanic", "Asian/Pacific Islander", "American Indian/Alaska Native" and "Not Specified". The group "Black" includes African American blacks, Haitians, Caribbean island blacks, Cape Verdeans, and others.

What are the risk behavior categories?
AIDS cases are categorized into one of eight risk behavior categories. These categories are:

  • Men who have sex with men (MSM)
  • Injection drug users (IDUs)
  • Men who have sex with men and inject drugs (MSM & IDU)
  • Recipients of blood or blood products (i.e. hemophiliacs and transfusion recipients)
  • Those who have heterosexual sex with an HIV-infected person or a person at increased risk for infection through MSM, IDU, receiving blood, etc.
  • Children born to HIV-infected mothers (perinatal transmission)
  • Those who have had a documented occupational exposure
  • Those with "No Identified Risk" (NIR) - Cases classified as NIRs have unknown risk(s), died or were lost to follow-up before risk was determined, or claim heterosexual exposure by do not know either the HIV status of their partner or reason for the partner's increased risk for HIV infection.

The numbers related to AIDS cases and the demographics of those with AIDS are important since they are one of the most direct ways of describing the AIDS epidemic in Massachusetts. However, numbers lose their meaning and value when they are not interpreted, or are interpreted incorrectly. Epidemiologists in the AIDS Surveillance Program are always available to provide and explain numerical information. For assistance, please call (617)983-6560.


This information is provided by the Bureau of Infectious Disease within the Department of Public Health.