Viral suppression occurs when there is an undetectable amount of HIV virus in a person's blood. A suppressed viral load is achieved when an HIV-positive individual is engaged in care and is able to adhere to an effective HIV drug regimen of antiretroviral therapy. The CDC estimates that, as of 2018, about 56% of HIV-positive people in the U.S. achieved viral suppression.
When viral load is not well suppressed, HIV can weaken the immune system, resulting in AIDS. A person with AIDS can develop life-threatening opportunistic infections and other serious conditions, such as wasting syndrome. A person is diagnosed with AIDS if they have HIV and one or more AIDS-defining conditions. The CDC has developed a list of opportunistic infections that are considered AIDS-defining conditions.