There is no need to imagine such a disease, because that disease is very real; it is called AIDS (acquired immunodeficiency syndrome). Since it was first mentioned in the medical literature in 1981, AIDS has spread into nearly every nation on earth and has caused more widespread panic, fear, and concern than any other medical catastrophe in the twentieth century. A new class of drugs, called protease inhibitors, appears to be prolonging the lives of most of those in the developed nations who are taking them. But whether they will remain effective is not yet clear. For the tens of millions of persons with HIV (human immunodeficiency virus) or AIDS in the developing world who cannot afford their prohibitive cost, the new drugs are not available. For them, AIDS is usually fatal, though we now have good reason to believe that a small proportion of those infected with the virus that causes AIDS will never develop symptoms and will not die from it. We also now know that some people who are repeatedly exposed to the virus will never become infected. But there is no easy way of knowing at this point who is immune and who is not, nor to yet harness that immunity for developing an effective vaccine for others.

The virus that causes AIDS is called HIV and is visible only with an electron microscope. It was first discovered by Dr. Louis Montagnier of France in 1983 and was called LAV. The following year, it was called HTLV-III by Dr. Robert Gallo of the United States, and then widely recognized as the cause of AIDS. It was renamed HIV two years later. The virus initially infects the body, sometimes producing flu-like acute symptoms, then remains dormant in the infected person's body for anywhere from two to twenty years (averaging about eight or nine years) before noticeable illness occurs. Since HIV breaks down the immune system of the infected person, almost anything can happen, and the person with AIDS is susceptible to developing serious illness from even the most commonplace microorganisms.

Symptoms include purplish or brownish blotches on the skin (caused by a cancer called Kaposi's sarcoma), severe coughing (caused by a deadly form of pneumonia called Pneumocystis carinii pneumonia, or by tuberculosis), vomiting, diarrhea, memory loss and senility (often called AIDS dementia), severe weight loss (often called the wasting syndrome), trembling (caused by toxoplasmosis), chronic tiredness, chronic fever, blindness (caused by cytomegalovirus retinopathy), swollen lymph glands, night sweats, white patches in the mouth and throat (called thrush), white bumps on the tongue (called oral hairy leukoplakia), and rows of painful blisters (called shingles or herpes zoster). Of course, few people with AIDS will have all of these symptoms. But clearly, experiencing the symptoms of AIDS is difficult and very unpleasant.

There are two distantly related viruses that cause AIDS: the more prevalent and more deadly HIV-1, which is found throughout the world, and the rarer and not nearly as lethal HIV-2, found mostly in West Africa. Unless indicated otherwise, when we refer to HIV in this book, we are referring only to HIV-1.

It is still not known how and where AIDS originated. Most probably HIV (that is, HIV-1) evolved naturally by mutating from either another, less lethal human virus or from a virus in an animal closely related to humans, such as an ape or monkey. In the mid-1980s it was thought that HIV mutated from the type of simian immunodeficiency virus (SIV) found in African green monkeys in central Africa. Today we know that is not true. Others have thought that HIV was brought to central Africa through mass polio inoculations conducted in the 1950s. The evidence for this is believed to be inconclusive at best. Others continue to believe that HIV is not natural at all, but was somehow concocted in the 1950s at a biological warfare lab, purposely to infect gay men, Africans, Haitians, injecting drug users, and others that the "government" did not like. However, those who are familiar with the capabilities of biological warfare labs in the 1950s believe that biotechnology at that time was not advanced enough to intentionally develop something as complex as HIV.

Some critics, such as virologist Dr. Peter Duesberg and the New York Native (a former gay weekly publication in New York City), have gone so far as to argue that HIV does not cause AIDS. They have claimed that AIDS may be caused by some other unknown pathogen (a disease-causing agent), or by too many drugs and too much sex overburdening the immune system. But today the evidence that HIV is the cause of AIDS is overwhelming. While it is true that other biological and sociocultural cofactors may influence the susceptibility to and the trajectory of HIV in producing AIDS, the fact that HIV is the cause of AIDS is unquestionable.

Some researchers believe that wild chimpanzees in central Africa, humans' closest relatives in the animal kingdom, are the source of HIV, but the evidence has not yet been established. Recently, work by researchers in Zambia suggests a possibility that a less deadly AIDS-like human illness common in parts of Zambia, Malawi, and may be elsewhere in central Africa may be the source from which HIV mutated a few decades ago. More research is needed to determine whether there is any truth to this. If we find out where HIV originated, it may help in developing a vaccine and be useful in better understanding the pattern of disease spread.

In any event, it is very likely that HIV did start somewhere in sub-Saharan Africa, because there are more subtypes of the virus on that continent than anywhere else in the world, and it is likely that the presence of these ten subtypes (also called clades) suggests a more diverse pattern of viral evolution that occurred over a long period of time. There is also reason to believe that AIDS affects a greater proportion of women and children through heterosexual transmission in Africa than in North America and Europe because of the nature of these more diverse subtypes, some of which may be more readily transmissible through semen and vaginal secretions. Only subtype B is common in North America and Europe, but as the other subtypes spread throughout the world, it is possible that the same pervasiveness of heterosexual transmission that is currently seen in Africa, India, Thailand, and other developing regions may become more visible in North America and Europe. The worldwide spread of AIDS is far from over. As frightening as it sounds, we may be only at the beginning of the epidemic as the various subtypes of HIV begin to enter new geographic areas. From the very beginning, the question of where HIV came from has been very politically charged. Bigots have used the question of the origin of AIDS to attack gays, Haitians, and Africans in order to promote their own racist or homophobic (gay-hating) agendas, attempting to have others believe that those who were first infected by the virus are somehow responsible for causing the virus. But viruses have no political agendas. They will spread and occasionally mutate when the opportunity arises, and their first casualties are no less innocent than their last casualties. Using the question of where AIDS originated to point the finger of blame at Africans or others is very destructive, mean-spirited, and absurd. There is virtually no question, however, where HIV-2 came from. It came from the type of SIV found in sooty mangabey monkeys in West Africa, and originally spread through people's eating infected monkey meat or skinning monkeys for their pelts and handling their infected blood. HIV-2 may have spread to humans even before HIV-1 did. Although HIV-2 can readily cause AIDS, evidence suggests that many, perhaps most, persons infected with it never develop any AIDS-related symptoms. HIV-2 has found its way to Brazil, France, and other countries. But, since it is much weaker than HIV-1, it is unlikely that its impact will be comparably significant. . .