I. INFECTION
The infection is caused by one of several related retroviruses that become incorporated into host cell DNA and result in a wide range of clinical diseases. These vary from asymptomatic carrier states to severe debilitating diseases that lead ultimately to death.
(My note on HIV: A retrovirus is tiny. After entering the cell, they make mirror images of their RNA by running backward, unlike the usual method to make a DNA version of their genes. They then insert themselves into vulnerable locations along the host DNA. The insertion at some points along the host DNA can release cancer potential in otherwise normal cells. All retroviruses contain an enzyme called reverse transcriptase that gives it its unusual and nasty potential.)
Two closely related viruses, HIV-1 and HIV-2 have been identified as causing AIDS in different geographic regions. HIV-1 causes most cases of AIDS in the Western Hemisphere. HIV-2 is less virulent and is the principal agent of AIDS in West Africa.
Some forms of HIV may not cause disease at all. Researchers are following a group of patients in Australia, so-called "nonprogressors" who have been infected with a single strain of HIV for more than 12 years with no sign of AIDS.
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II. TRANSMISSION
Contact with body fluids containing infected cells or plasma is required. These include blood, semen, vaginal secretions, breast milk, or saliva contaminated with blood. Prior to testing, HIV was transmitted by blood products, including 'factor' for hemophiliacs. Transmission by saliva, coughing, or mosquitoes has NOT been documented. HIV is not spread by casual contact.
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III. AIDS IN AMERICA
The first reports of a new disease among gay men in Los Angeles appeared in 1981. Quickly, similar reports came from San Francisco and New York. Staid heterosexual researchers quickly learned of bath houses and those very active homosexuals with more than 200 different contacts a year. Since 1975, there had been an alarming increase of all sexual diseases among members of the gay community in California. Early on, an immunodeficiency was observed in this new category of gay-related diseases. Specifically, T-helper cells in the immune system seemed to disappear as the disease progressed.
The first name for the new disease was GRID: Gay Related Immunodeficiency Disease. Early studies found it was greatest amongst persons with many partners in big cities who were anal receptive. By 1982, with the body count rising, physicians, researchers, and gay activists in France and the United States mobilized research programs.
When CDC investigators tried to track down the 'trail' of sexual contacts among gay persons with GRID, a strange thing happened. Several mentioned a handsome male French-Canadian flight attendant.
The name of that alleged first patient, Gaetan Dugas, was leaked to reporter Randy Shilts. After Dugas' death he would be vilified as 'patient zero,' the man who first spread the epidemic in North America. He is estimated to have had 2500 sexual partners since becoming active in 1972. It is NOT certain that he was truly 'patient zero.'
In 1981, several persons from Haiti were identified with GRID and this led to finger pointing: unjustly accusing a specific immigrant group for the epidemic. But, early in 1982, a new group of people were showing up with GRID: hemophiliacs who used Factor VIII made from the pooled plasma of thousands of donors. GRID was no longer a gay disease. The CDC switched the name to Acquired Immune Deficiency Syndrome-AIDS.
Remarkably, no serious survey of the nation's blood supply was undertaken until 1984. Advances in surgery had also increased the demand for blood. By 1987, heat treatment had rendered Factor VIII safe again, but at a cost per dose increase from $90. to $1000.
Competition (and hostility) developed between the French and American research groups. By 1985, the HIV (virus) was also made available. Scientists in 1985 thought a vaccine and an effective treatment couldn't be far away.
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IV. ORIGINS IN AFRICA
Sorting out the origins of AIDS is not easy. HIV is a slow acting virus, spreading insidiously, infecting its victims sometimes without obvious symptoms for 12 years or more. The earliest documented cases of AIDS now date from 1959. Frozen blood samples taken then from a Zairean man later proved to be infected by HIV. Also that year, AIDS is believed to have killed a 25 year old British sailor. His doctors were mystified by the sailor's illness, and only in 1986 did they determine, by testing a preserved sample of his tissue, that he was HIV positive.
There are many theories on the origin of HIV. One is that HIV may have originated between 50 and 100 years ago in some part of Central or West Africa, where several species of monkeys carry a closely related virus called simian immunodeficiency virus or SIV. At some point, the disease made the jump to human beings, perhaps when someone was bitten by an infected monkey.
HIV may have been present in remote regions of Central Africa for a long time, just infecting small numbers of people. The social customs of traditional village life limited the spread of HIV and other sexually transmitted diseases, since extramarital and premarital trysts were condemned and virtually impossible in the claustrophobic cultures of tiny communities scattered throughout equatorial Africa.
The paving of the highway from Kinshasa in Zaire to Mombasa on the Indian Ocean may have helped to open the way for the HIV virus to spread. Along it are full service establishments with food, beer, bed, and a woman. Medical doctors who work in East Africa believe that 90% of the prostitutes working along the road carry HIV.
(My note: 40 or so prostitutes who work in the slums on the outskirts of Nairobi in Kenya seem to be immune to HIV. For years they have been continually exposed to HIV, yet they remain free of any trace of the virus. Tests reveal no antibodies or the viral organism. They appear to have specialized cells that can kill off the virus before it can inflict any damage. Curious researchers are mapping their genes to learn how this happens.)
Urbanization and its resulting erosion of traditional sex taboos and lifestyles may be the key to the emergence of HIV in Africa. Urban centers are an ecosystem than can amplify infectious contagious diseases.
AIDS in Africa did not spread simply because the virus was present. The change in the interaction between the agent, the host and the environment is usually required for the epidemic. Social change, including the effects urbanization and population movements contribute movements contribute to the rapid spread of the AIDS virus. One study has shown that in one remote area, the number of people infected has remained low over the last ten years. It took an urban environment and all that goes with it to allow the HIV epidemic to explode.
Old World monkeys carry the HIV-like viruses. New World monkeys do not carry them. The discovery of the monkey AIDS viruses date back to the earliest days of the recognized human epidemic, when scientists with the California Primate Research Center at Davis noted similarities between disease symptoms experienced by gay men and those seen in four strange disease outbreaks among monkeys at their facilities. The first outbreak occurred in 1969. It lasted for six years. During that time, 42 monkeys suffered lymphomas and a host of opportunistic infections related to severe T-cell immune system depression.
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V. MOLECULAR BIOLOGY AND THE ORIGIN OF HIV
As the technology of analyzing genetic material improved during the 1980s it became possible to compare all of the various monkey and human HIV viruses nucleotide by nucleotide, noting where similarities and differences existed. Using such techniques, scientists would begin to construct family trees for the viruses. They were doing lineages of evolution that resemble those used by paleoanthropologists who study evolution.
At the heart of the technique, which is called molecular epidemiology were a few key assumptions: the more alike two viral genetic were, the more likely it was that they shared a common and recent ancestor. This is like Darwin's finches on the Galapagos Islands. With them, Darwin had concluded, the similarity implied a common finch ancestor.
Like human evolution, viral evolution takes time. The degrees of viral variation could be correlated with a timetable of years or centuries. If you are following this--it is similar to the 'Eve hypothesis' discussed in human evolution.
There are certain genetic features that were so essential to the survival of HIVs and SIVs (simian immune virus, the 'monkey version' of HIV) that they would be conserved over generations of viruses.
The essential conclusion (you are following this, aren't you?) Was that is was UNLIKELY that human virus had evolved into monkey virus. The family tree had to have begun with SIV. Each of these assumptions would be challenged in time, but the basic approach would survive criticism.
How close are human and monkey viruses? SIV and HIV were close, sharing more than 75% homology (similarity). HIV-1 had only a 40% homology with either virus. Some strains of HIV-2 and SIV were so similar that scientists concluded that monkey to human transmission had occurred since World War II.
There is one notable exception to the pattern of HIV distribution in human beings: Pygmies. For millennia the Pygmy people had lived in the dense rain forests of Cameroon, Congo, and the Central African Republic, surviving as the continent's most expert jungle hunters. Monkey meat had always been a part of the Pygmy diet, and the people (particularly male hunters) had frequent and often violent contact with the monkey populations.
You would expect Pygmies to have been exposed to monkey SIV. Such SIV infections have occurred amongst handlers of monkeys who were scratched, bitten, or had needle sticks here in the United States. Blood tests of Pygmy volunteers revealed no cases of HIV-2 or HIV-1 infection. Here is a reminder in case you have forgotten: HIV-2 is the one prevalent in Africa; HIV-1 is here in the United States.
HIV-1 has become such a genetically specialized human killer that scientists were at pains to find ways to infect laboratory monkeys and apes with it. They could not produce clear-cut AIDS in any nonhuman primate. Natural carries (monkeys in Africa) of the various SIVs that they harbored were unharmed by those viruses.
When viral strains collected in a given geographic location over a period of years were compared, the GenBank study group found that HIV-1 was evolving (mutating) at an overall rate of 1 percent a year. This is astonishing when you consider that mitochondrial DNA used in the Eve hypothesis studies mutates at only 2-4% every million years! Nuclear DNA mutates much more slowly.
Studies of the mutation of HIV-1 suggests that some change took place in the disease epidemiology about 1975 in Central Africa. Scientists refer to this as the 'big bank' theory in HIV origins. Not everyone endorses this idea.
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VI. OTHER THEORIES ON THE ORIGIN OF HIV
Some suggest that HIV-1 got to people by way of vaccines. At the head of the suspect list is the idea that HIV accompanied a batch of live polio vaccine prepared with African green monkey kidney cells. These vaccines were dispersed in Africa from 1957-1960. Surviving samples have been tested. They were free of HIV.
Another more elaborate theory involves the campaign to eliminate smallpox. It claimed that latent, ancient HIV infections were activated when people were vaccinated against smallpox. This theory came from a British journalist, not qualified scientists.
One renowned evangelist believes that "AIDS was an inevitable punishment for sexual deviance, a judgement of God." Is this homophobia--the fear of homosexuals?
A few persons on the fringe of credibility have claimed that HIV is the work of the KGB or even the CIA--as germ warfare. Knowledgeable people in the field reject all of this as nonsense.
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VII. EPILOGUE
In retrospect, social conditions in 1979-1980 were clearly ripe for the emergence and spread of even an extremely rare virus. Humans being beings have done it to themselves, one observer has said. Veterans, victims of rape, and prostitutes fled from the Tanzanian/Ugandan war in search of living in nearby urban centers. Truck routes along that roadway in Africa through the former war zone fueled the spread of HIV via roadside brothels. Plane travel made HIV international.
The emergence of HIV in North America was likely driven along by the overlapping injecting-drug using gay male population. The homosexual population generally had good incomes and access to health care. In contrast, the injecting/drug using population was generally outside of the medical system. With them, the early stages in the epidemic would have been out of sight of health workers.
During that time period, STDs (sexually transmitted diseases) exploded in North America, Europe, and Africa. Multiple partner sexual activity had increased. Needles produced in massive numbers for medical purposes aided and abetted the spread of AIDS as many found their way to the drug injecting population. The time was ripe, conditions were ready, and HIV spread explosively. As they say, the rest was history.
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VIII. QUEST FOR A CURE
The search for a comprehensive treatment for AIDS faces the challenge of the virus's capacity for rapid and radical mutation. The first drug that showed success against the virus was AZT, a drug that began as a chemotherapy agent for treatment of cancer. The newest class of drugs are the protease inhibitors used in a 'triple cocktail' therapy. These treatments are not a cure. the HIV virus reappears when treatment is stopped.
The end of AIDS is far from being in sight. A major problem is money. A year of treatment with triple combination drugs can cost between $10,000. and $16,000, and far more if the patient is in hospital at the same time. These costs simply cannot be paid by impoverished Third World countries with health budgets of $1. to $10. per person per year. Even comparatively rich Thailand (prior to the recent currency problems) which spends only about $30. per person per year on health care.
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VIII. POSTSCRIPT 20 September 1999
These are abstracts of two current articles about AIDS. Similar articles under different titles appeared in other periodicals.
(From Waldholz, M. "AIDS Spreading to Teenage Girls in Parts of Africa" Wall Street Journal September 15, 1999. HIV is being spread to girls in sub-Saharan Africa by sex with infected older men. The study reported that between 15% and 23% of girls were HIV positive, while only 3% to 4% of boys in the same age group were infected. STDs, particularly syphilis and herpes greatly increase susceptibility to HIV infection. The motives for sex with older men are often economic: some girls even do it to pay for school supplies.)
(From Waldholz, M "Number of AIDS Deaths Drops 20%, But Pace of Decline Slows Significantly" Wall Street Journal August 31, 1999. The death rate from AIDS have fallen significantly since 1995 when the powerful multi drug treatment regimens were introduced. The rate of decline, however, tapered off in 1998. Several reasons may account for the slowing decline: drug resistance, persons who discontinue drug treatment, and persons in whom drug treatment is simply ineffective.))
..... CJ '99
Resources
Brookesmith, P. Biohazard: The Hot Zone and Beyond. New York. Barnes & Noble Books, 1997.
"Earliest AIDS infection have have occurred in the '40s" Chicago Tribune February 4, 1998.
Garrett, L. The Coming Plague. New York: Farrar, Straus and Giroux, 1994.
"Viruses" National Geographic. July, 1994, pp 58-91.
Underwood, A. "How the Plague Began" Newsweek Februay 8, 1999.