Why the incubation period to develop AIDS takes several years?

The transition time for HIV developing into AIDS takes time because it is dependent on the virus mutating to a form which allows itself to bind the CXCR4 chemokine receptor, in addition to the CCR5 receptor. Once the virus is able to bind (and hence gain entry into the cell) both receptors, AIDS begins to develop.

This is when the Tcell count begins to drop and professional antigen presenting cells (in the case of CXCR4--macrophages and dendritic cells) are affected by the virus. As a result one's immune system begins to deteriorate rapidly.

There is a big difference between a HIV diagnosis and an AIDS diagnosis. HIV is the virus that can cause AIDS, but with medications people who have been infected with HIV can live a long time before it turns into an AIDS diagnosis.

There are many people who have become infected with HIV but because they do not test for the virus, they are not aware they are infected with the virus. This can take 10-12 years for a healthier person.

A diagnosis of AIDS is based on T-cell count, if the T-cells are above 200+ the person is HIV+ once it drops below 200 then it becomes an AIDS diagnosis. Once again with the medications for some one who is HIV+ people are living a lot longer and may never have an AIDS diagnosis.

The important thing to note, is if a person is infected with HIV they need to test early and get into a treatment program. If they eat right, get plenty of rest, exercise and take their meds as prescribed, they can live a great life.