HIV destroys CD4 cells (also called T cells). CD4 cells are part of the immune system. They fight germs and help prevent some kinds of cancers.
How Is HIV Diagnosed?
Health care providers usually diagnose HIV through blood tests. Someone who has HIV is said to be "HIV positive."
Tests also are available without a prescription at the drugstore. You can do the test at home.
How Is AIDS Diagnosed?
HIV is diagnosed as AIDS when someone:
has fewer than 200 CD4 cells or
develops an AIDS-defining condition
How Are HIV and AIDS Treated?
Medicines can help people with HIV stay healthy. They can also prevent HIV from progressing to AIDS.
Health care providers prescribe a combination of different medicines for people with HIV and AIDS. They must be taken exactly as prescribed or they won't work. These medicines:
help keep the number of CD4 cells high
reduce the viral load of HIV (how much HIV is in the body)
Regular blood tests will check the number of CD4 cells in the body (called the CD4 cell count) and the viral load.
If an HIV-positive person's CD4 count gets low, doctors prescribe daily antibiotics. This prevents pneumocystis pneumonia, which happens in people with weakened immune systems.
Can HIV Be Prevented?
To reduce the risk of getting HIV, people who are sexually active should:
use a condom every time they have sex (including vaginal, oral, or anal sex)
get tested for HIV and make sure all partners do too
reduce their number of sexual partners
get tested and treated for STDs (sexually transmitted diseases); having an STD increases the risk of HIV infection
consider taking a medicine every day (called PrEP or pre-exposure prophylaxis) if they are at very high risk of getting infected (for example, if they are in a sexual relationship with someone with HIV)