A person living with HIV is considered to have developed AIDS when their immune system is so weak it can no longer fight off certain opportunistic infections and diseases, such as pneumonia, meningitis, and some cancers. One of the most common opportunistic infections among people living with HIV/AIDS is tuberculosis (TB).
Despite the availability of affordable rapid tests for HIV, knowledge of HIV status remains low in sub-Saharan Africa where HIV prevalence is highest.
An estimated 60 percent of people living with HIV are unaware of their status and in some settings this figure is far lower; a study in Kenya in 2009, for example, found that only 16 percent of HIV-infected adults knew that they were infected.