Primary infection is the first step in the course of HIV infection. After HIV enters the host cell, it starts replicating itself intensively and is widely disseminated throughout the body, with the lymphoid organs becoming seeded with the virus. There is a significant drop in CD4 T cells at this early time. Flu-like symptoms are common and 50 - 75% of patients develop this acute mononucleosis-like syndrom.

Approximately one to three months after infection a specific immune response develops, causing the number of viral particles to decrease and the CD4 cell count rebounces. However, the immune response is unable to clear the infection completely, and HIV-infected cells persist in the lymph nodes as viral DNA integrated in the host genome. This period of clinical latency may last for as long as 10 years, but there is still a a high level of ongoing viral replication.

Eventually, clinically apparent diseases develop, such as neoplasms or opportunistic infections. These are a consequence of rapid viral proliferation in CD4 infected cells and their subsequent destruction which weakens the immune system. The onset of these symptoms is known as the progression to AIDS.

Despite enormous efforts to find the ultimate cure for AIDS there is no efficient treatment that could totally eliminate HIV. The main reason for not being able to develop a useful drug is the lack of proofreading replication enzymes in HIV. Consequently, mutations occur changing the properties of HIV molecules. Thus, resistance evolves quickly, making many existing drugs useless. Nevertheless, certain therapeutics and drug cocktails can slow down AIDS progression and provide better life for those infected with HIV. Another problem in AIDS treatment is the price of therapeutics; only a fraction of infected population can afford the expensive treatment.