AIDS is the most severe form of the HIV infection. An infected HIV patient may seem healthy and not notice symptoms for years.

Biologically, HIV is an RNA retrovirus, It integrates into the target cell genome as a provirus, then begins the replication and dividing process. The RNA virus contains the enzyme reverse transcriptease, which is capable of making a DNA copy of the viral RNA. There are six total genes present. The genome contains the RNA in a dense characteristic cylindrical core. Moreover, it contains an outer lipid envelope about 100 nm in diameter.

Testing for HIV detects the antibodies at the core p24, envelope gp41, and segment gp120 locations. A negative HIV antibody test means there were no antibodies found at this time. However, HIV may take up to three to six months to have detectable antibodies. There are two different tests widely used. The ELISA test is performed twice for accuracy. If a positive result is received, it is then confirmed by the Western Blot or IFA tests.

HIV has a specific pathogenesis. It binds to the target call, enters the cell, and then is uncoated. The genomic RNA is transcribed into DNA by the reverse transcriptease. Protein synthesis follows the transcriptease. The new DNA is integrated into the host genome. The replication cycle is restricted at this stage until activated by other pathogens.

The period from infection to the developing of serious symptoms may take up to 10 years. The "cycle" may progress slowly or rapidly along the spectrum. A number of factors may influence the progression rate. At various positions along the spectrum, certain health concerns appear and different treatments become appropriate. Lab tests on the immune system indicate what treatments and medicinal strategies are appropriate. These medicinal treatments can slow HIV progression and prevent complications.