Most of us are used to thinking of disease in very simple terms: if you feel sick, you are sick; if you feel healthy, you are healthy. However, because HIV may be causing subtle changes in the immune system long before an infected person feels sick, most doctors have adopted the term "HIV Disease" to cover the entire HIV spectrum, from initial infection to full-blown AIDS (which can also be called "Advanced HIV Disease").

The continuum that follows and its stages are representative of the experience of many people with HIV. The time that it takes for each individual person to go through these stages is varied. For most people, however, the process of HIV disease is fairly slow, taking several years from infection to the development of severe immunodeficiency.

HIV enters the bloodstream and begins to take up residence in the cells. People with HIV are considered to be infectious immediately after infection with the virus. Although some studies suggest that the level of infectivity varies over time depending on the stage of the disease in which the person is, it is not possible for most HIV-infected people to find out what their level of infectivity is.

A person with HIV is infectious at all times. Also, a person does not need to have symptoms or look sick to have HIV. In fact, people may look perfectly healthy for many years despite the fact that they have HIV in their bodies. The only way to find out if a person is infected is by taking an HIV antibody test.

Primary HIV infection is the first stage of HIV disease, when the virus first establishes itself in the body. Some researchers use the term acute HIV infection to describe the period of time between when a person is first infected with HIV and when antibodies against the virus are produced by the body (usually 6- 12 weeks). Within the first 72 hours after exposure, post exposure prevention (PEP) may be possible.

Up to 70% of people newly infected with HIV will experience some "flu-like" symptoms. These symptoms, which usually last no more than a few days, might include fevers, chills, night sweats and rashes (not cold-like symptoms). The remaining percentage of people either do not experience "acute infection," or have symptoms so mild that they may not notice them.

Given the general character of the symptoms of acute infection, they can easily have causes other than HIV, such as a flu infection. For example, if you had some risk for HIV a few days ago and are now experiencing flu-like symptoms, it might be possible that HIV is responsible for the symptoms, but it is also possible that you have some other viral infection.

During acute HIV infection, the virus makes its way to the lymph nodes, a process which is believed to take three to five days. Then HIV actively reproduces and releases new virus particles into the bloodstream. This burst of rapid HIV replication usually lasts about two months. People at this stage often have a very high HIV "viral load." However, people with acute HIV infection usually will not test HIV antibody positive, since it takes the body approximately one to three months to produce antibodies against HIV.

Scientists disagree about whether anti-HIV treatment is useful during primary HIV infection, and there is little information from clinical trials. Most HIV specialists believe that early highly active antiretroviral therapy (HAART) is useful, and that its benefits likely outweigh the disadvantages of no treatment.

This term refers to the time when the body begins producing antibodies to the virus. About 95% of the people infected with HIV will develop antibodies within three months after infection. Nearly all people will develop antibodies within six months after infection.

Most people develop antibodies within three months and some can take up to six months. People who get tested need to wait at least three months for the test. If their first result is negative, they should come back for a second test three months later.