Ailments and Situations - Acquired Immune Deficiency Syndrome or AIDS - Infection Stages

There are six clinical stages of HIV infection. These stages are based on the CD4+ T cell count, CD4+ T cell function, the presence of or stage of lymphadenopathy, skin tests, and the presence of opportunistic infections.

Stage 0 represents the time of initial infection. This stage can be asymptomatic (without symptoms), or can be accompanied by mild, flu-like, symptoms. It is often misdiagnosed as the flu or infectious mononucleosis, with fever, swollen lymph nodes, fatigue, and perhaps a rash. These symptoms last only a few weeks at most while this stage can last a few weeks or up to a year. During this time, a large number of CD4+ T cells are infected and killed by HIV and a large number of viral particles are produced. The body produces anti-HIV antibodies and a person is then said to "seroconvert". The immune system is able to clear the virus from circulation and reduce infection of new cells. By the end of this stage, CD4+ T cell numbers usually return close to normal levels.

The next stage begins with the diagnosis of HIV infection. A person in Stage 1 is said to be "seropositive" for the anti-HIV antibody (the antibody is found in their blood), or simply "HIV positive". People are usually asymptomatic during this stage, but some may begin to experience various central nervous system disorders ranging from headaches to encephalitis. These symptoms often disappear within a few weeks. At this point, only a small percentage of CD4+ T cells in the bloodstream are infected with HIV and most of them have only one copy of the viral genome in a latent state. HIV continues to actively replicate, however, in lymphoid tissue, brain and intestinal cells, and other sites of the body.

HIV continues to destroy lymphoid tissue and the thymus gland and the immune system is chronically activated by HIV. This continues to gradually deplete the body of CD4+ T cells in a manner yet unknown. We are now at Stage 2 of infection, which is marked by lymphadenopathy lasting for more than 2 months (chronic). The enlargement of the lymph glands is due to over-stimulation of B cells. This leads to the production of a large number of non-functional antibodies. Stage 2 can last anywhere from three to five years.

During stage 3, there is a persistent drop of CD4+ T cell numbers to less than 400/mm³ of whole blood (normal numbers are approximately 550/mm³ of whole blood). This stage usually lasts approximately eighteen months.

Stage 4 is characterized by the impairment of "cell-mediated immunity" and is demonstrated by the failure to respond to three of four routine skin tests. Cell-mediated immunity refers to the part of the immune response initiated by T cells and mediated by T cells and/or macrophages.

Stage 5 entails the development of "anergy". Anergy denotes the inability of the body to generate a sensitivity or allergic reaction to substances that it should react to, or has known to be reactive to in the past. This stage can last one to two years and is often marked by the presence of thrush and other viral or fungal infections.

Stage 6 refers to the presence of opportunistic infections. The patient's CD4+ T cell count is extremely low (100/mm³ of whole blood or less). Most patients die within two years of the beginning of this stage.

In all, it can be ten or more years that pass between initial HIV infection and death caused by an opportunistic infection in AIDS. Efforts are geared towards turning AIDS into a chronic disease instead of a terminal illness. A number of scientists are trying to create an HIV vaccine, but are having great difficulty as HIV mutates so rapidly. In fact, it has been found that no two viral isolates from the same person contain the same genetic material, likening this rapid sort of mutation to that of a cold or flu virus.