The three stages of an HIV infection are acute infection, clinical latency and acquired immunodeficiency syndrome, also referred to as AIDS. The infected individual can spread the disease at any stage, according to AIDS.gov.
The first stage of infection, acute infection, starts about 2 to 4 weeks after the initial exposure to the virus, explains the Centers for Disease Control and Prevention. Not every infected person experience symptoms during the acute infection, but many do. During this phase, the virus multiplies inside immune cells called CD4 cells and destroys them, causing a rapid decrease of these cells and the development of flu-like symptoms.
Once the immune system has brought the virus under control, and the number of CD4 cells stabilizes once again, the symptom-free period called clinical latency begins, states AIDS.gov. During this stage of HIV infection, the infected person doesn't usually display symptoms. The clinical latency phase can last 10 years or more.
A person with HIV enters the last stage, AIDS, when the number of CD4 cells in each cubic milliliter of blood drops below 200 or when the immune system has become compromised enough that opportunistic infections develop, explains AIDS.gov. Proper HIV treatment can help slow the progression from one stage to the next, and antiretroviral therapy, or ART, may prevent an infected individual from ever progressing into full-blown AIDS.