In a nutshell, despite the fact that HIV is a slow-acting virus, it has a fatal effect on the immune system because with time the latter is eventually unable to produce sufficient antibodies to fight off any opportunistic infection. The incubation period of AIDS lasts an average of about 8 years. Patients tested HIV-positive will eventually have the following specific toxic responses: loss of appetite, weight loss, fever, night sweats, skin rashes, diarrhea, tiredness, lack of resistance to infection, and swollen lymph nodes. Those who have developed AIDS would have more severe symptoms. Usually, it is another opportunistic disease, not the HIV per se, that ultimately cause death. There is evidence showing that some cofactors such as nutrition, stress, and previous sexually transmitted diseases can have an effect on HIV infection.

An in-depth discussion of HIV infection and its effects on the immune system is beyond the scope of this lecture. Nonetheless, it is important to note that even though there has no cure yet for AIDS or HIV infection, some effective therapies appear to be available for prolonging the life of AIDS patients or delaying the onset of fetal opportunistic infections in AIDS patients. One treatment method is the use of antiretroviral drugs to reduce the viral load in the body. Another method is the use of drugs that can delay certain fatal opportunistic infections. The important point being made here is that, it is toxicological tools and concepts that were used to discovery HIV as the eventual causative agent of AIDS. Without this knowledge, anti-viral or anti-opportunistic drugs would not have been made available these days.