Below you can learn more about the data methods and sources for the state and county data on AIDSVu. Looking for data methods and sources for ZIP code or census tract data? Click here.

HIV Surveillance Data

The HIV prevalence data presented on AIDSVu are collected by state and local health departments, and de-duplicated and processed by the U.S. Centers for Disease Control and Prevention (CDC) to meet data quality standards for comparability and reliability. All 50 states, the District of Columbia (DC) and U.S. territories collect comparable confidential, name-based case reports of persons living with an HIV infection diagnosis following standard methods and procedures. Medical providers and other organizations providing HIV testing services are required, by law, to report persons diagnosed with HIV to the state or local health department. Health departments report case data without names to CDC for monitoring of the national HIV epidemic.

All state- and county-level HIV surveillance data for AIDSVu were obtained from CDC’s national HIV surveillance database housed in the Division of HIV Prevention's HIV Incidence and Case Surveillance Branch. Data were released to AIDSVu by CDC in accordance with HIV-surveillance-specific data re-release agreements between CDC and each state/U.S. territory health department, and in accordance with other CDC data release guidelines. Data reflected on AIDSVu may slightly differ from data obtained directly from state HIV surveillance programs (e.g., on a state health department website or through a data request to a state surveillance program) because states may use analysis criteria that are different from what AIDSVu used (e.g., analyzing data by “current residence” versus “residence at earliest HIV diagnosis”). Further, data on AIDSVu may differ from data obtained directly from the states because AIDSVu’s data source was CDC’s national HIV surveillance database, from which duplicate records are removed. AIDSVu also displays ZIP code and census tract data for a small number of jurisdictions (cities or Metropolitan Statistical Areas). More information about where these data come from and their presentation on AIDSVu can be found here.

All state- and county-level HIV surveillance data displayed on AIDSVu maps and state profile pages are estimated data for persons aged 13 and older living with an HIV infection diagnosis as of December 31, 2009. Estimated numbers resulted from statistical adjustment that accounted for reporting delays and missing risk-factor information, but not for incomplete reporting. Estimates are based upon actual data reported to CDC through June 2011. (See CDC methodology for estimating HIV prevalence.) Residence at time of earliest HIV diagnosis was used in all analyses. Denominators used to calculate 2009 rates for all state and county populations were obtained from official post-2000 census estimates from the U.S. Census Bureau. Population denominators are restricted to persons aged 13 and older. There are no counties in Alaska, the District of Columbia or Puerto Rico.

Estimated rates of persons living with an HIV diagnosis were calculated per 100,000 population to permit data standardization and comparison. As is standard in the display of health statistics, rates generated from a numerator less than 12 are considered unstable and should be interpreted with caution. To determine if a specific state or county meets this criterion, place the mouse cursor over the state or county and, in the balloon that appears, there will be a message noting that a rate meets this condition, if applicable. For estimated rate ratios by race/ethnicity displayed on state profile pages, white race is the referent group.

For those states and jurisdictions that have name-based HIV reporting systems that have been operating for less than four years (DC, HI, MD, MA, VT), data were not provided by CDC and therefore are not displayed on the state and county maps. Surveillance data from these systems cannot be adjusted to account for reporting delays and, therefore, estimated data comparable to that of other states cannot be calculated. For this same reason, AIDSVu is not able to display the “estimated percent of late HIV infection diagnoses,” “estimated rate ratios by race/ethnicity,” and “estimated cases by transmission category” for these states/jurisdictions. In 2013, all states/jurisdictions will have mature name-based HIV reporting and will be reflected on AIDSVu’s state- and county-level maps, as permitted by the states.

Data Suppression and Rate Stability

To protect the privacy of persons living with an HIV infection diagnosis, AIDSVu does not display rates and case counts for states and counties when one or more of the following suppression criteria are met:

1) Numerator (number of persons living with an HIV infection diagnosis) is less than 5 and/or the denominator (number of people in the state or county in that population group) is less than 100.

2) For breakdowns by sex at the county level, if either the male or female rate and/or case count is suppressed because of the numerator/denominator thresholds mentioned in #1, both sex groups are suppressed to prevent indirect identification.

3) For breakdowns by age at the county level, if the rate and/or case count for only one age group is suppressed in a county because of the numerator/denominator thresholds mentioned in #1, then the 13-19 age group is also suppressed to prevent indirect identification. If the 13-19 age group is the only age group suppressed for a county, then the 55+ age group is also suppressed.

4) If all data for only one county in a state is suppressed, then one additional county is also suppressed, with the additional county selected based on the fact that it has the smallest total population of the remaining counties.

States and counties appear white when one or more of these conditions are met.. Because rates are not displayed when the numerator is less than 5, the “unstable rate” indicator mentioned above will only display when the numerator is 5 or greater and less than 12.

Data Stratification

AIDSVu allows viewers to look at state- and county-level HIV surveillance data at the overall geographic level, and by race/ethnicity, sex and age groups. Additionally, AIDSVu displays state-level HIV prevalence data by transmission category. All race groups are non-Hispanic, and the Hispanic/Latino ethnicity is inclusive of all races. Sex is defined as “sex at birth.” Cases were assigned to age groups based on “age at the end of 2009.” Caution should be exercised when viewing and interpreting these different maps because the scales change across the different breakdowns and geographic levels; the correct scale is always displayed to the left of the map regardless of the breakdown.

Data are not displayed at the county level for Asians, Native Hawaiians/Other Pacific Islanders, and American Indians/Alaska Natives because these data do not meet CDC’s criteria for statistical reliability, data quality or confidentiality due to small population denominators and HIV case counts by county. Race/ethnicity data for Puerto Rico is displayed only by case counts (and not by rate) because the U.S. Census does not produce post-decennial population estimates by race/ethnicity for U.S. territories.

Displayed Ranges

Range intervals were developed using deciles in SAS analytic software (SAS Institute, Cary, NC). In order to illustrate the variation in rates and case counts, ranges were developed specific to each geographic level (i.e., states or counties), and for each grouping (i.e., overall, and separately by race, by sex and by age group). Thus, for state maps, a total of 12 sets of map scales exist (rate/count by overall/race/sex/age/male transmission category/female transmission category). For county maps, a total of eight sets of map scales exist (rate and count, both by overall/race/sex/age). For each scale calculation, we determined deciles by combining the individual rates or counts for all areas with data included on the maps for that geographic level and grouping.

Social determinants of health are displayed on a secondary map and their associated scales were developed using quartiles. Quartiles for each social determinant were determined individually using the same procedure described above. Therefore, there are 10 additional ranges for these data (i.e., five social determinants for both state and county levels).

Corrections Warning

The data displayed on AIDSVu include state and federal correctional populations. Their inclusion may artificially inflate the HIV prevalence rate and case count of counties that house institutions. A correctional warning is displayed in the map hover-over balloon of certain counties when artificial inflation may be present based on predefined criteria.

To determine in which counties the correctional warning should appear, the following process and predefined thresholds were used to categorize counties.

1) All U.S. counties were categorized by level of urbanization using the National Center for Health Statistics (NCHS) Urban-Rural Classification Scheme.

2) Federal and state correction populations were obtained for each county from the 2010 U.S. Census.

3) Within these strata of urbanization, counties are assigned the corrections warning if they had:

• Above average HIV prevalence rate (as compared to counties with no correctional population), and
   
• Above average correctional population or above average percent of the population housed in state/federal correctional institutions.

Data Sources - Surveillance Data

HIV Testing, Treatment and Prevention Information, and Federal Funding for HIV/AIDS

Social Determinants of Health

State Health Department Websites and Contacts