Data Methods

Learn more about the data that informs AHEAD.

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The HIV data presented on this site are from the National HIV Surveillance System (NHSS), managed by the Centers for Disease Control and Prevention (CDC). NHSS is the primary source for monitoring HIV trends in the United States. The CDC funds and assists state and local health departments to collect the information. States and local jurisdictions, including the District of Columbia and Puerto Rico, have laws or regulations that require confidential reporting by name for adults and adolescents (i.e., persons aged 13 and older) with a confirmed HIV diagnosis. After the removal of personally identifiable information, data from these reports are submitted to CDC. Health departments report these de-identified data to CDC so that information from around the country can be analyzed to determine who is being affected and why, which can inform where HIV prevention and treatment resources are most needed.

Data on diagnoses of HIV infection should be interpreted with caution. Data may not be representative of all persons with HIV because not all infected persons have been tested. Also, many states offer anonymous testing; the results of anonymous tests are not reported to the confidential name-based HIV registries of state and local health departments. The data presented on this site provide minimum number of persons for whom HIV infection has been diagnosed and reported to NHSS. In addition, because surveillance practices differ, the reporting and updating of a person’s clinical and vital status differ among states.

The NHSS data displayed on this site may not be comparable to surveillance data published by individual jurisdictions. This is because: (1) CDC de-duplicates cases at the national level, and (2) national data have been statistically adjusted to account for missing transmission category. For more information, please refer to the the CDC fact sheet at the following link:

The baseline year for HIV surveillance data used for calculating most of the Ending the HIV Epidemic (EHE) indicators (incidence, diagnoses, knowledge of status, linkage to care, and viral suppression) is 2017.

Data for calculating the baseline indicator for HIV Preexposure Prophylaxis (PrEP) coverage include 2017 data from IQVIATM pharmacy database for estimating the number of persons prescribed PrEP, as well as 2017 data from NHSS, National Health and Nutrition Examination Survey, and American Community Survey for estimating the number of persons with indications for PrEP.

Definitions for each indicator can be found at the following pages: