HIV drugs keep the virus from multiplying in the body, which benefits the person with HIV and prevents transmission of the virus to others.
Research has firmly established that people with HIV who achieve and maintain an undetectable viral load—the amount of HIV in the blood—by taking HIV treatment as prescribed cannot transmit the virus during sex. An undetectable viral load also reduces the risk of HIV transmission during pregnancy, labor, and delivery to 1% or less, according to the Centers for Disease Control and Prevention. It also substantially decreases, but does not eliminate, the risk of HIV transmission through breastfeeding.
People with HIV sometimes get other illnesses and complications related to HIV, even when the virus is well-controlled with treatment. These include co-infections like hepatitis C and tuberculosis, as well as non-infectious complications such as heart disease. People with advanced-stage HIV may develop serious opportunistic infections, like pneumocystis pneumonia or cryptococcal disease. There are treatments available for many of these other illnesses.
The National Institute of Allergy and Infectious Diseases has more information about HIV treatment research.