What are we measuring?
HIV, or human immunodeficiency virus, attacks the body’s CD4 cells (T cells), which help the immune system fight off infections.  If left untreated HIV can lead to the disease AIDS (acquired immunodeficiency syndrome).  AIDS is the stage of infection that occurs when your immune system is badly damaged and you become vulnerable to opportunistic infections.  A new HIV diagnosis is defined as a diagnosis of HIV infection regardless of the stage of disease (stage 0, 1, 2, 3 [AIDS], or unknown) and refers to all persons with a diagnosis of HIV infection during the the latest year for which data are available.  This is a measure of incidence and is not to be confused with HIV prevalence, which is a measure of the number of persons living with diagnosed HIV.
Why are we measuring it?
Incidence rates are the most useful data to determine how well the HIV/AIDS epidemic is being controlled.  A declining rate of new diagnoses indicates some success in efforts to prevent new infections and serves as a gauge for the effectiveness of current prevention programs.  
How are we doing?
The rate of new HIV diagnoses per 100,000 residents for Fulton County dropped from 90 in 2008 to 76 in 2016; however, Fulton County continues to have among the highest rates in the U.S. and has the highest rate among U.S. counties with 1 million or more people.