HIV, or human immunodeficiency virus, is a lentivirus, which means that it is slow-acting. HIV symptoms appear at two distinct stages, and understanding these times, as well as HIV's long latency period, are key to understanding the virus.
Primary Infection
Some people experience mild, flu-like symptoms one to two weeks after becoming infected, while others experience no symptoms at all. Even people who do develop a flu-like condition will experience no further symptoms for a long time.
Latency
HIV is a lentivirus, so named for the long stretch of time after acute (primary) infection in which there is an absence of symptoms. This does not mean that the virus is inactive or that it is not possible to spread it to others during this time. On the contrary, during latency the virus is slowly attacking the body's immune defenses by targeting T cells.
Because HIV targets immune cells, the body becomes increasingly unable to fight off HIV and other infections. Most people with HIV became infected through contact (unprotected sex, sharing needles) with a person who was in the latent phase of infection.
AIDS
AIDS (Acquired Immune Deficiency Syndrome) is said to develop when an infected person's CD4 (a type of T cell) count is below 200. At this point, the immune system is no longer able to cope with the virus, and a series of opportunistic infections (so named because they do not affect people with healthy immune systems) develop. These include pneumocystis pneumonia, thrush and Kaposi's sarcoma. AIDS normally develops within 10 to 15 years after primary infection, although it can take 20 years or more. AIDS also develops much more rapidly in some individuals, though the use of antiretroviral therapies can help delay its onset.
Identification
The first cases of HIV infection were found among people who had already developed AIDS because the initial symptoms of HIV are very mild or absent, and there was, at the time, no test for HIV. However, once HIV was isolated as the root cause of AIDS, it became possible to test for the virus. Today, some tests, which search for HIV RNA (the genetic code of the virus) can detect the virus within two weeks of infection. Other tests are used to screen for antibodies to the virus. Developing a detectable level of antibodies to HIV (seroconversion) often happens within about one month after infection, though the process can take as long as six months.
Considerations
Because early HIV infection is often principally asymptomatic, regular screening for it is one of the most important ways to control the spread of the virus and ensure that infected individuals receive appropriate treatment. The use of antiretroviral drugs has improved the life expectancy and quality of life of those infected.
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