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For several years after seroconversion, people with HIV infection feel good. Because they have no symptoms of the infection, this period is called the asymptomatic (meaning “no symptoms”) period. During this period the person will be unaware of the HIV infection unless a blood test shows antibodies to HIV. About 70-80 percent of the people who presently have HIV infection are in this asymptomatic period.
The length of time people remain in the asymptomatic period is highly variable. The average is five to eight years until the symptoms of HIV infection appear, and eight to ten years until AIDS is diagnosed. The shortest time, two years or less from infection until the development of AIDS, is highly unusual. Most people stay asymptomatic for five years or more. Based on four different studies (done before any effective treatment was available), the time lapse between transmission of HIV and AIDS is as follows: After 1 year, 0 percent of the people with HIV infection were diagnosed with AIDS; after 2 years, 0 percent; after 3 years, 3 percent; after 4 years, 6 percent; after 5 years, 12 percent; after 6 years, 20 percent; after 7 years, 27 percent; after 8 years, 36 percent; after 9 years, 45 percent; after 10 years, 53 percent.
The reasons for this great variation are unknown. We know that treatment makes a decisive difference in the rate of the infection’s progression. We would like to think that “wellness”—a psychological sense of well-being, good nutrition, exercise programs, and other general health measures—increases the length of the asymptomatic period, although we don’t know that.
Other factors may contribute to the length of the asymptomatic period but are beyond the control of the person with HIV infection. One of these factors is the inoculum size, or number of viruses when infection took place: the lower the inoculum size, the slower the infection
progresses. Another factor is the specific strain of the virus: some strains of HIV seem to cause the infection to progress faster. A third factor is the age of the person infected: the infection progresses much faster in children and somewhat faster in older people. The final factor is the genetic makeup of the person infected: some people seem to have genes that make them prone to faster progression of the infection.
The presumed reason for the long delay before symptoms appear is the body’s enormous number of CD4 cells (the white blood cells that help the immune system and that the virus infects). At first, the virus infects only a relatively small number of CD4s, then more and more of them, but the process is slow. Several years go by before the body loses so many
CD4s that the immune system cannot defend itself against other infections. Most people lose about 80 to 90 percent of their CD4s before AIDS develops.

Transmission of HIV
Acute infection
Asymptomatic period
AIDS-related Complex, or ARC
The effects of HIV infection on the body have been studied thoroughly. Many studies have followed people who engage in high-risk behaviors, from before they were infected, through the entire course of the infection, to the final stage of AIDS. We now know the usual course of HIV infection with considerable precision.
In most people, HIV infection follows a clear course: transmission of the virus is followed by an acute infection that clears up spontaneously; then there is a prolonged period during which the person feels good and has no symptoms of infection, that is, is asymptomatic; the person
gradually develops the symptoms that are sometimes called AIDS-related complex, or ARC; eventually, the person develops the disease referred to as acquired immune deficiency syndrome, or AIDS, which is defined by the presence of a variety of other infections in many different parts of the body, the so-called opportunistic infections.
Based on extensive studies, researchers have determined the duration, on average, of each stage. Individual people, however, spend widely varying amounts of time in each stage. Some people with positive HIV blood tests have remained healthy for over ten years, though most have declining numbers of CD4 cells, suggesting some suppression of the immune system.
The course of HIV infection is generally as follows:
Transmission of HIV, usually by blood exposure or through sexual intercourse.
Two to six weeks: Acute infection, meaning the development of an infectious
mononucleosis-like illness from which people recover in one or two weeks. Some people do not even notice this stage.
Four to twelve weeks, sometimes longer: Seroconversion, that is, the body develops antibodies to HIV, and as a consequence, the results of the blood test for the presence of antibodies to HIV are positive.
Asymptomatic interlude, during which the person feels well and functions normally except for the psychological stress that accompanies knowledge of a positive test.
Five to eight years, with considerable individual variation: symptoms of AIDS-related complex, or ARC. Some people never develop ARC but progress directly to AIDS.
Eight to ten years: AIDS as defined by diagnosis of an opportunistic infection, opportunistic tumors, or AIDS dementia.