Data Methods – ZIP Code/Census Tract

Expand one of the categories below to learn more about the data methods and sources for the ZIP code and census tract data on AIDSVu. Looking for data methods and sources for state or county data? Click here.

ZIP Code Data

To permit the display of HIV prevalence data by ZIP code, AIDSVu obtained a data release agreement with health departments overseeing HIV surveillance in the following jurisdictions: Atlanta, Chicago, Dallas, Detroit, Hampton Roads, Houston, Los Angeles, Memphis, Miami, New Orleans, New York City, Orlando, Philadelphia, San Diego, San Francisco, San Juan, Tampa, and Washington, DC. Data were obtained directly from the public health departments rather than from the U.S. Centers for Disease Control and Prevention (CDC) because CDC does not collect street addresses for reported cases, and street addresses are required for mapping at the ZIP code level. Because data were not obtained directly from CDC, ZIP-code-level data are not directly comparable to the state- and county-level HIV prevalence data also displayed on AIDSVu.

Each public health department defined the geographic area (e.g., ZIP codes) in their jurisdiction for which they desired to display data on AIDSVu.  ZIP-code-level HIV surveillance data reflect persons living with an HIV or AIDS diagnosis in the defined geographic area as of December 31, 2010. For details regarding each jurisdiction’s assignment of ZIP codes to cases missing an address at diagnosis, or to cases where the ZIP code at diagnosis has changed because of the redrawing of ZIP code boundaries, see the Data Caveats table below. Denominators used to calculate rates for ZIP codes were obtained from the U.S. Census Bureau’s 2010 census of ZIP Code Tabulation Areas (ZCTAs). Additional information on ZCTAs can be found here.

AIDSVu allows viewers to look at ZIP-code-level HIV surveillance data at the overall geographic level, and by race/ethnicity, sex and age groups. The black, white and Asian/Pacific Islander race groups are non-Hispanic, and the Hispanic/Latino ethnicity is inclusive of all races. Sex was defined as “sex at birth.” Cases were assigned to age groups based on age at the end of 2010. Caution should be exercised when viewing and interpreting the ZIP code maps because the scales change across the different breakdowns; the correct scale is always displayed to the left of the map, regardless of the breakdown.

Rates of persons living with an HIV/AIDS diagnosis were calculated per 100,000 population to permit data standardization and comparison. For ZIP codes that house correctional institutions, caution should be exercised when interpreting the data as these statistics are inclusive of institutional populations and their inclusion may artificially inflate the actual rate and case count of a ZIP code when an institution is housed in it. 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. If a specific ZIP code meets one or both of these conditions, , there will be a message in the balloon that appears when you place your mouse cursor over the ZIP code noting that a correctional facility is located in the ZIP and/or that the rate is unstable .

To protect the confidentiality of persons living with an HIV/AIDS diagnosis, AIDSVu does not display rates and case counts when the numerator (number of persons living with an HIV/AIDS diagnosis) is less than 5 and/or the denominator (number of people in the ZIP code in that population group) is less than 500. ZIP codes appear in a shade of gray when one or both of these conditions are met (see footnote below map scale). Because rates are not displayed when the numerator is less than 5, the “unstable rate” indicator mentioned above will only be displayed when the numerator is 5 or greater, but less than 12.

Range intervals were developed using deciles in SAS analytic software (SAS Institute, Cary, NC) and are based on the combined data of all jurisdictions providing ZIP-code-level data so that comparisons can be made across cities. In order to illustrate the variation in rates and case counts, ranges were developed specific to each grouping (i.e., overall, by race/ethnicity, by sex and by age group). Thus, 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 each ZIP code 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 4 additional ranges for these data (i.e., four social determinants for overall ZIP code level).

Jurisdiction-Specific Data Caveats

Jurisdiction Data Caveats
Atlanta Data reflect cases entered through 04/01/2013 and are based on residence at diagnosis as reported in Georgia’s Electronic HIV/AIDS Reporting System (eHARS). Data reflect cases from ZIP codes in Clayton, Cobb, DeKalb, Douglas, Fulton and Gwinnett Counties. Cases missing ZIP code at diagnosis are excluded from the analysis.
Charlotte Data reflect cases from all of Mecklenburg County, not just the city of Charlotte Data are for cases reported through 4/18/2013 and are based on residence at diagnosis. Only ZIP codes for residences in Mecklenburg County, N. C. with greater than 50% of their population within the county boundary are included. Cases with no ZIP code entry are not included.
Chicago Data reflect cases reported through 02/15/2012. Homeless cases and those cases missing an address at diagnosis were omitted. Cases with an address at diagnosis and no ZIP code data were geocoded to obtain ZIP code information.
Dallas Data reflect cases reported through 04/03/2012.  Any cases missing ZIP code at diagnosis were excluded from analysis.
Denver Data reflects cases reported through 12/31/2012. All ZIP codes that overlap another county besides the five county metro area have been included. For homeless individuals, the facility of diagnosis’s zip code is used.
Detroit Data reflect cases reported through 01/01/2013. Rates for Wayne County, including the City of Detroit, are not displayed because of the inability to accurately assess population size. Rates for this map would have been calculated by dividing the number of individuals diagnosed with HIV in a given ZIP code by the total population living in that ZIP code according to the 2010 census. However, persons living with HIV in 2010 were diagnosed in Wayne County between 1981 and 2010. Because of the sharp population decline in Wayne County (especially in Detroit – 25 percent decline since 2000), the 2010 census population numbers do not accurately reflect the population during the years when these individuals were diagnosed, thus the accuracy of rates would be uncertain.Cases missing ZIP code (including homeless persons) are few (20 cases) and not included. Corrections facilities in Wayne County are jails with relatively short stays and persons diagnosed in jail are mapped using their home addresses.Highland Park and Hamtramck are cities within the City of Detroit. They are considered part of Wayne County, but since they share ZIP codes with the City of Detroit, their ZIP codes are labeled as Detroit ZIP codes.
Hampton Roads Data reflect cases reported through 04/07/2013 and are based on residence at diagnosis. For a ZIP code crossing boundaries to another jurisdiction outside of the Hampton Roads, only the Hampton Roads cases are included in the data. Cases missing ZIP code (including homeless persons) are excluded from this analysis.
Houston Data reflect cases reported through 03/25/2012. For a ZIP code sharing jurisdiction of Houston/Harris County and other jurisdiction(s), only the Houston/Harris County cases are reflected in the data.
Los Angeles County Data reflect cases reported through 12/31/2011. When ZIP code information for residence at diagnosis was not available, the most recently reported residential ZIP code that was within the L.A. County jurisdiction was assigned.
Memphis Data reflect cases reported through 12/31/2011.  Any cases missing ZIP code at diagnosis were excluded from analysis.
Miami (Miami-Dade, Broward and Palm Beach Counties) Data represent persons reported and alive with an HIV or AIDS diagnosis in Miami-Dade, Broward and Palm Beach Counties at the end of 2010 as of 03/27/13.   Data for this area will be reflected in 3 separate maps, one for each county.
New Orleans Data reflect cases reported through 4/9/2012. New Orleans experienced a significant population decrease following Hurricane Katrina in August 2005, particularly in selected ZIP codes that experienced significant flooding. Prevalence rates in the following Orleans Parish ZIP codes are inflated: 70112, 70113, 70116, 70117, and 70125.
New York City Data represent persons diagnosed with HIV or AIDS in New York City and not known to have died as of 12/31/2010 and who were reported as of 09/30/2011. Only residential ZIP codes were included in the analysis. Cases with unknown ZIP code at HIV/AIDS diagnosis or with ZIP code outside NYC were excluded.
Orlando Data represent persons reported and alive with an HIV or AIDS diagnosis in Lake, Orange, Osceola and Seminole Counties at the end of 2010 and reported as of 03/27/13.
Philadelphia Data reflect cases reported through 12/31/2012. Cases without ZIP code for residence at diagnosis were excluded.
San Diego Data represent persons living with an HIV or AIDS diagnosis in San Diego at the end of 2010
San Francisco Data reflect cases reported through 03/05/2013. Data are displayed for the city and county of San Francisco and include Treasure Island. All addresses at HIV/AIDS diagnosis were geocoded using the most current street and ZIP code shapefile to validate ZIP codes provided at time of report. Cases with discrepant ZIP code information were closely examined. If the street address was valid, the updated ZIP code was assigned. Otherwise, if the street address could not be verified, the ZIP code was left unchanged. Corrected ZIP codes were also assigned to cases with previously missing ZIP codes at time of diagnosis. Usual residence was determined for cases diagnosed in a correctional facility. If a usual residence could not be determined, the case would have an unknown San Francisco address because these cases were not assigned the correctional facility address at time of diagnosis; there are not inflated numbers in ZIP codes with correctional facilities. Homeless cases are not displayed on the map.
San Juan – Caguas – Guaynabo, MSA, PR Data reflect cases reported through 11/14/2012.  Cases with missing address information at HIV/AIDS diagnosis were excluded from analyses.  Only data from San Juan – Caguas – Guaynabo MSA are displayed on the maps.
Tampa Data represent persons reported and alive with an HIV or AIDS diagnosis in Hernando, Hillsborough, Pasco and Pinellas Counties at the end of 2010 and reported as of 03/27/13.
Washington, DC Data reflect cases reported through 12/31/2012. ZIP code data include name-based cases. Cases with missing address information at diagnosis were not included in this analysis. Cases diagnosed in a correctional facility were assigned the ZIP code of the correctional facility. Homeless cases with addresses of a shelter at diagnosis were assigned to the ZIP code of the homeless shelter.

Data Sources

Data Element Location on AIDSVu Data Source Anticipated Update Frequency on AIDSVu Website
Rates and Case Counts of Persons Living with an HIV Diagnosis, ZIP Code Data Maps California Department of Public Health, Surveillance, Research, and Evaluation Branch, Office of AIDSChicago Department of Public Health, STI/HIV Division, Surveillance, Epidemiology and Research Section

Colorado Department of Public Health and Environment, Disease Control and Environmental Epidemiology

District of Columbia Department of Health, HIV/AIDS, Hepatitis, STD and TB Administration

Florida Department of Health, HIV/AIDS and Hepatitis Section

Georgia Department of Public Health, Division of Health Protection, Epidemiology Program, HIV/AIDS Epidemiology Section

Houston Department of Health and Human Services, Office of Surveillance and Public Health Preparedness

Los Angeles County Department of Public Health, Division of HIV and STD Programs, HIV Epidemiology

Louisiana Office of Public Health, STD/HIV Program

Michigan Department of Community Health, Michigan HIV/STD/VH/TB Epidemiology Section

New York City Department of Health and Mental Hygiene, HIV Epidemiology and Field Services Program

North Carolina Department of Health and Human Services, Communicable Disease Branch

Philadelphia Department of Public Health , AIDS Activities Coordinating Office

Puerto Rico Department of Public Health, Division of HIV/AIDS

San Francisco Department of Public Health, HIV Epidemiology Section, HIV Surveillance Unit

Tennessee State Department of Health, HIV/AIDS/STD Surveillance and Management

Texas Department of State Health Services, TB/HIV/STD Epidemiology & Surveillance Group

Virginia Department of Health, Division of Disease Prevention, HIV/AIDS Surveillance Program

Annually
Population Denominators for Rate Calculations Maps U.S. Census Bureau, 2010 Census Summary File 1 (Dataset SF-1, Tables PCT12, PCT12B, PCT12D, PCT12E, PCT12H, PCT12I) Based on availability of data.
HIV Testing Sites Maps; HIV Testing Site Locator Centers for Disease Control and Prevention, National Prevention Information Network; Ongoing Data Access Request. Daily
Ryan White HIV/AIDS Medical Care Providers Maps; HIV Treatment Site Locator Health Resources and Services Administration, HIV/AIDS Bureau; Data Request, April 2012. Annually
NIH-Funded HIV Prevention, Vaccine and Treatment Trials Sites Maps National Institutes of Health, National Institute of Allergy and Infectious Diseases, Division of AIDS; Data Request, March 2013. Annually
Poverty (Percent of population, all ages, living in poverty) – Zip Code Level Maps U.S. Census Bureau, American Community Survey 5-Year Estimates, 2007-2011,  Table S1701: Poverty Status in the Past 12 Months Annually
Educational Attainment (Percent of people over age 25 with at least a high school diploma or equivalent) – Zip Code Level Maps U.S. Census Bureau, American Community Survey 5-Year Estimates, 2007-2011, Table S1501: Educational Attainment Annually
Median Household Income – Zip Code Level Maps U.S. Census Bureau, American Community Survey 5-Year Estimates, 2007-2011, Table S1903: Median Income in the Past 12 Months Annually
Gini Coefficient of income inequality – Zip Code Level Maps U.S. Census Bureau, American Community Survey 5-Year Estimates, 2007-2011, Table B19083: Gini Index of Income Inequality Annually

Census Tract Data

To permit the display of census-tract-level HIV prevalence data, AIDSVu obtained a data release agreement with the public health departments overseeing HIV surveillance in Atlanta, Washington, DC and Philadelphia. Data were obtained directly from the public health departments and not from CDC because CDC does not collect street addresses for reported cases, and street addresses are required for mapping at the census tract level. Because of this, census-tract-level data are not directly comparable to the state- and county-level HIV prevalence data also displayed on AIDSVu.

Census-tract-level HIV surveillance data reflect persons living with an HIV infection or AIDS diagnosis as of December 31, 2010. Residence at earliest HIV or AIDS diagnosis was used in the assignment of cases to census tracts. For more information on how these two jurisdictions handle the assignment of a census tract to cases missing an address at diagnosis, see the Data Caveats table below. Denominators used to calculate rates for census tracts were obtained from the U.S. Census Bureau’s 2010 census of census tracts.

AIDSVu allows viewers to look at census-tract-level HIV surveillance data at the overall geographic level, and by race/ethnicity, sex and age groups. The black and white race groups are non-Hispanic, and the Hispanic/Latino ethnicity is inclusive of all races. Sex was defined as “sex at birth.” Cases were assigned to age groups based on age at the end of 2010. Caution should be exercised when viewing and interpreting the census tract maps because the scales change across the different breakdowns; the correct scale is always displayed to the left of the map, regardless of the breakdown.

Rates of persons living with an HIV/AIDS diagnosis were calculated per 100,000 population to permit data standardization and comparison. For census tracts that house correctional institutions, caution should be exercised when interpreting the data as these statistics are inclusive of institutional populations and their inclusion may artificially inflate the actual rate and case count of a census tract when an institution is housed in it. 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.

If a specific census tract meets one or both of these conditions, there will be a message in the balloon that appears when you place your mouse cursor over the census tract noting that a correctional facility is located in the census tract and/or that the rate is unstable.

To protect the confidentiality of persons living with an HIV/AIDS diagnosis, AIDSVu does not display rates and case counts for census tracts when the numerator (number of persons living with an HIV infection diagnosis) is less than 5 and/or the denominator (number of people in the census tract in that population group) is less than 500. Census tracts appear in a shade of gray when one or both of these conditions are met (see footnote below map scale). Because rates are not displayed when the numerator is less than 5, the “unstable rate” indicator mentioned above will only be displayed when the numerator is 5 or greater, but less than 12.

Scale intervals were developed using deciles in SAS analytic software and are based on the combined data of the two jurisdictions providing census-tract-level data so that comparisons can be made between cities. In order to illustrate the variation in rates and case counts, ranges were developed specific to each grouping (i.e., overall, by race/ethnicity, by sex and by age group). Thus, 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 each census tract, including all levels of race/ethnicity, sex or age, when applicable.

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 4 additional ranges for these data (i.e., four social determinants for overall census tract level).

Jurisdiction-Specific Data Caveats

Jurisdiction Data Caveats
Philadelphia Data reflect cases reported through 12/31/2011. Census tracts were assigned based on residence at diagnosis (when available), or earliest residence reported.
Washington, DC Data reflect cases reported through 12/31/2011. Census tract data includes both code-based and name-based cases. Cases with missing address information at diagnosis were not included in this analysis. Cases diagnosed in a correctional facility were assigned the census tract of the correctional facility. Homeless cases with addresses of a shelter at diagnosis were assigned to census tracts of the homeless shelter.
Atlanta Data reflect cases entered through 04/01/2013. Census tracts were assigned based on residence at diagnosis (when available), or earliest residence reported.  Cases diagnosed in a correctional facility were assigned the census tract of the correctional facility. Homeless cases with addresses of a shelter at diagnosis were assigned to census tracts of the homeless shelter.

Data Sources

Data Element Location on AIDSVu Data Source Anticipated Update Frequency on AIDSVu Website
Rates and Case Counts of Persons Living with an HIV Diagnosis, Census Tract Data Maps District of Columbia Department of Health, HIV/AIDS, Hepatitis, STD and TB AdministrationGeorgia Department of Public Health, Division of Health Protection, Epidemiology Program, HIV/AIDS Epidemiology SectionPhiladelphia Department of Public Health , AIDS Activities Coordinating Office Annually
Population Denominators for Rate Calculations Maps U.S. Census Bureau, 2010 Census Summary File 1 (Dataset SF-1, Tables PCT12, PCT12B, PCT12D, PCT12E, PCT12H, PCT12I) Based on availability of data.
HIV Testing Sites Maps; HIV Testing Site Locator Centers for Disease Control and Prevention, National Prevention Information Network; Ongoing Data Access Request. Daily
Ryan White HIV/AIDS Medical Care Providers Maps; HIV Treatment Site Locator Health Resources and Services Administration, HIV/AIDS Bureau; Data Request, April 2012. Annually
NIH-Funded HIV Prevention, Vaccine and Treatment Trials Sites Maps National Institutes of Health, National Institute of Allergy and Infectious Diseases, Division of AIDS; Data Request, March 2013. Annually
Poverty (Percent of population, all ages, living in poverty) – Census Tract Level Maps U.S. Census Bureau, American Community Survey 5-Year Estimates, 2007-2011,  Table S1701: Poverty Status in the Past 12 Months Annually
Educational Attainment (Percent of people over age 25 with at least a high school diploma or equivalent) – Census Tract Level Maps U.S. Census Bureau, American Community Survey 5-Year Estimates, 2007-2011, Table S1501: Educational Attainment Annually
Median Household Income – Census Tract Level Maps U.S. Census Bureau, American Community Survey 5-Year Estimates, 2007-2011, Table S1903: Median Income in the Past 12 Months Annually
Gini Coefficient of income inequality – Census Tract Level Maps U.S. Census Bureau, American Community Survey 5-Year Estimates, 2007-2011, Table B19083: Gini Index of Income Inequality Annually