The stages of HIV infection are acute infection (also known as primary infection), latency, and AIDS. Acute infection lasts for several weeks and may include symptoms such as fever, swollen lymph nodes, inflammation of the throat, rash, muscle pain, malaise, and mouth and esophageal sores. The latency stage involves few or no symptoms and can last anywhere from two weeks to twenty years or more, depending on the individual. AIDS, the final stage of HIV infection, is defined by low CD4+ T cell counts (fewer than 200 per μL), various opportunistic infections, cancers, and other conditions.
Acute HIV infection, primary HIV infection or acute seroconversion syndrome is the second stage of HIV infection. It occurs after the incubation stage, before the latency stage, and the potential AIDS succeeding the latency stage.
During this period (usually days to weeks post-exposure) fifty to ninety percent of infected individuals develop an influenza or mononucleosis-like illness called acute HIV infection (or HIV prodrome), the most common symptoms of which may include fever, lymphadenopathy, pharyngitis, rash, myalgia, malaise, mouth and esophageal sores, and may also include, but less commonly, headache, nausea and vomiting, fatigue, ulcers in the mouth or on the genitals, enlarged liver/spleen, weight loss, thrush, night sweats and diarrhea and neurological symptoms. Infected individuals may experience all, some, or none of these symptoms. The duration of symptoms varies, averaging 28 days and usually lasts at least a week.
Because of the nonspecific nature of these symptoms, they are often not recognized as signs of HIV infection. Even if patients go to their doctors or a hospital, they will often be misdiagnosed as having one of the more common infectious diseases with the same symptoms. As a consequence, these primary symptoms are not used to diagnose HIV infection, as they do not develop in all cases and because many are caused by other more common diseases. However, recognizing the syndrome can be important because the patient is much more infectious during this period.