Data Methods

Learn more about the data that informs AHEAD.

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On this Dashboard, values for the EHE indicators are stratified – at the national level only – by the following demographic characteristics: age, race/ethnicity, sex at birth (for incidence, knowledge of status, and PrEP coverage), gender (for diagnoses, linkage to HIV medical care, and HIV viral suppression), and transmission category. Overall total values (unstratified) are presented at the national, state/territory, and county levels for all indicators.

Age Groups

The data shown on this site are only for adults and adolescents (i.e., persons aged 13 years and older with PrEP being the exception of 16 years and older). For diagnosis data, age is based on the person’s age at HIV diagnosis. For data on persons living with diagnosed HIV, the age is based on the person’s age as of December 31 of the queried year. Ten-year age groups are used with HIV surveillance data to ensure data security and confidentiality.


Data are generally grouped into the following racial/ethnic categories (each race category is non-Hispanic): American Indian or Alaska Native, Asian, Black or African American, Hispanic or Latinx, Native Hawaiian or other Pacific Islander, White and multiracial. Persons of Hispanic/Latinx ethnicity can be of any race.

PrEP data has different race/ethnicity categories due to the source of the data. The categories for PrEP are: Black/African American, Hispanic/Latinx, Other, and White.

Some HIV prevalence cases are missing information on the individual’s race/ethnicity. These unknown racial/ethnic groups are not displayed. Therefore, if you summarize the data by race/ethnicity, they may not match the national totals overall.

Sex and Gender

Sex designations (male and female) on this Dashboard are based on a person’s sex assigned at birth. National-level data for the following indicators are stratified by sex (information on gender is not available) and include transgender persons: incidence, knowledge of status, and PrEP coverage.

The term gender in this Dashboard refers to gender identity – a person’s internal understanding of their gender, or the gender with which a person identifies – and includes the following categories: male, female, transgender male-to-female, transgender female-to-male, and other gender identity (e.g., bigender, gender queer, two-spirit, non-binary). National-level data for the following indicators are stratified by gender: diagnoses, linkage to HIV medical care, and HIV viral suppression.

Transgender is an umbrella term that is used to identify persons whose sex assigned at birth does not match current gender identity or expression. Transgender male-to-female refers to people who were assigned male sex at birth but have ever identified as female gender. Transgender female-to-male refers to individuals who were assigned female sex at birth but have ever identified as male gender. In May 2013, CDC issued guidance to state and local programs on methods for collecting data on transgender persons and working with transgender-specific data. Information on gender identity is still not consistently collected or documented in the data sources used by HIV surveillance reporting jurisdictions. Thus, HIV data by gender remain limited. HIV surveillance personnel collect data on gender identity, when available, from sources such as case report forms submitted by health care or HIV testing providers and medical records, or by matching with other health department databases (e.g., Ryan White program data).

Transmission category

Transmission category is the term for the classification of cases that summarizes a person’s possible HIV risk factors; the summary classification results from selecting, from the presumed hierarchical order of probability (riskiest behavior), the one risk factor most likely to have resulted in HIV transmission. The exception is men who had sexual contact with other men and injected drugs; this group makes up a separate transmission category.

Persons whose transmission category is classified as male-to-male sexual contact include men who report sexual contact with other men and men who report sexual contact with both men and women.

Persons whose transmission category is classified as injection drug use (IDU) are persons who injected non-prescribed drugs.

Persons whose transmission category is classified as heterosexual contact are persons who have ever had specific heterosexual contact with a person known to have, or with a risk factors for, HIV infection (e.g., a person who injects drugs).

All other transmission categories have been collapsed into “Other.” The “Other” transmission category includes: hemophilia, blood transfusion, perinatal exposure, and risk factor not reported or not identified.

Due to the large number of cases reported without transmission category information, transmission category data are statistically adjusted using multiple imputation techniques to account for missing transmission category information in cases reported to CDC. Because of this statistical adjustment, the values across individual transmission categories may not sum to the national totals for incidence, knowledge of HIV status, linkage to HIV care, diagnoses, and HIV viral suppression.

For more details, please refer to the following sources:

  1. Terms, Definitions, and Calculations Used in CDC HIV Surveillance Publications. Centers for Disease Control and Prevention.
    Terms, Definitions, and Calculations | Surveillance Overview | Statistics Center | HIV/AIDS | CDC Updated 2019. Accessed May 14, 2021.
  2. Harrison KM, Kajese T, Hall HI, Song R. Risk factor redistribution of the national HIV/AIDS surveillance data: an alternative approach. Public Health Rep 2008;123:618–27.