Germs, Genes, & Civilization: How Epidemics Shaped Who We Are Today

by David P. Clark

  Another curious example of a venereal disease that arose from a bloodborne disease is a trypanosome disease of horses. Trypanosoma evansi is a relative of sleeping sickness that infects horses. Normally, it is spread by bloodsucking flies, but a specialized venereal strain exists in South America that is spread during mating. Entry requires a local break in the skin surface—that is, blood contact. Such minor skin lesions occur quite frequently when horses mate.

  Origin of AIDS among African apes and monkeys

  The earliest known sample of HIV was found in blood taken in 1959 from an inhabitant of the Belgian Congo (now the Democratic Republic of the Congo). HIV mutates rapidly and at a fairly predictable rate. Comparison of different early strains, including the 1959 sample and another from 1960, suggest that the HIV ancestor appeared around 1890–1920 and had already diverged into different variants well before the AIDS epidemic emerged into public view.

  HIV is closely related to SIV (simian immunodeficiency virus), which is found in assorted apes and monkeys. The whole SIV/HIV group of viruses is relatively new. African monkeys living in Africa frequently carry viruses of this family. In contrast, monkeys of African origin living on Caribbean islands do not carry SIV. The ancestors of the Caribbean monkeys were brought from Africa in the 1600s and 1700s, implying that SIV was not in widespread circulation at that time.

  Two groups of human immunodeficiency viruses are known. The original, HIV-1, accounts for the vast majority of cases and is the most virulent. HIV-2 is relatively rare and is less virulent. The ancestor of HIV-1 was probably transferred to humans from chimpanzees in the equatorial region of West Africa. Three subtypes of HIV-1 are known at present that probably derive from separate transfer of closely related viruses from chimp to human. HIV-2 seems to have branched off independently from the SIV family and entered the human population later, probably via the sooty mangabey monkey.

  Viruses of the SIV family are still being transferred to humans in Africa. Infection usually happens during butchering of chimpanzees and monkeys for meat or, less often, from keeping them as pets. Several cases of newly transferred SIV have been found in recent years by screening blood samples from Africans. Most SIV strains cause little harm either to their original hosts or to humans who acquire them. Likewise, chimpanzees do not suffer from AIDS, even if deliberately infected with HIV-1 from humans. Very rarely, newly transferred SIV strains can mutate rapidly inside the human host, so generating dangerous novel variants. That is, they can become new HIV strains.

  Worldwide incidence and spread of AIDS

  In the United States, just over a million people are infected with HIV. The epidemic appears to have stabilized, with about 50,000 new infections per year. New AIDS cases mostly result from homosexual transmission, with smaller contributions from intravenous drug use and heterosexual transfer. In the United States, deaths from AIDS dropped from around 50,000 in 1995 to about 16,000 in 2002 as a result of improved therapy.

  In rich nations, AIDS is restricted to a small subpopulation and has not entered the mainstream. But in the Third World, AIDS is vastly more widespread. About 60 million people are infected with HIV worldwide, two-thirds of these in Africa. By 1999, there were 2.7 million deaths due to AIDS worldwide, with 2.2 million in Africa. AIDS has now overtaken tuberculosis and malaria as the leading cause of death among infectious diseases, with about three million deaths per year. The real numbers of AIDS victims may be higher. Just as deaths from syphilis were often recorded as “consumption” in Victorian England, in Africa, social stigma has resulted in AIDS deaths often being officially attributed to tuberculosis.

  In industrial nations, about 20% of AIDS victims are female, compared to 50% in the Third World. Several factors affect HIV transmission in the Third World that have little effect in advanced nations. One is the effect of other venereal diseases. To cause disease, HIV needs to enter the bloodstream and invade the white blood cells. Crossing the thin intestinal wall is much easier for most viruses than crossing the vaginal lining. Consequently, anal intercourse is much riskier than vaginal intercourse. The risk of heterosexual AIDS transmission is greatly increased if the victim is already infected with another venereal disease that damages the surface of the genital organs. HIV can then reach the bloodstream via breaks in the skin.

  Much heterosexual AIDS transmission in Third World nations occurs in people who already have other venereal diseases. In poor nations, these often go untreated. Even in advanced nations, the risk of HIV infection is much greater for those already infected with herpesvirus. Another reason Africa has been hit so hard by AIDS is that infestation by parasitic worms, which is widespread in poor African countries, also makes victims much more susceptible to AIDS.

  In poor countries AIDS is also transmitted by contaminated needles. Poor Third World countries cannot afford disposable medical supplies. Reusing needles or other instruments, which are often improperly sterilized, spreads AIDS. It has even been suggested that vaccination programs against other diseases have contributed significantly to spreading AIDS in Africa. Obviously men, women, and children are at equal risk from this mechanism, regardless of sexual behavior. Most such cases are listed as “heterosexual spread” partly through ignorance and partly to avoid responsibility and embarrassment by the local regimes.

  Sharing dirty needles also spreads AIDS among intravenous drug addicts in advanced nations. In most European nations, clean sterile needles are available to drug addicts. Consequently, addicts rarely pass AIDS and other blood-borne diseases such as hepatitis to each other. In the United States, antidrug legislation has targeted everything remotely associated with drugs. Although the drug supply has scarcely been affected, such legislation makes obtaining clean needles more difficult. Consequently, American drug addicts more often share used needles and so spread AIDS to a greater extent than in other industrial nations. Although needle-exchange programs now operate in some U.S. states, there are still fewer of them than in Europe.

  The Church, morality, and venereal infections

  “It is worse to preach immorality than practice it.”—Italo Svevo

  Ancient epidemics were often hailed as the judgment of God. Venereal diseases have consistently been regarded as divine displeasure with sexual immorality. In early medieval Europe, the Church theoretically forbade prostitution. In practice, however, prostitution was tolerated. Bathhouses, some run by civic authorities—even the Church itself—operated in many European cities. Many were flimsy covers for prostitution. Medieval cities often restricted prostitution to certain districts and often prescribed special garb for prostitutes, such as yellow scarves or scarlet sashes.

  During the early to mid-1500s, bath houses and brothels were shut down all over Europe as the Catholic Church took aggressive measures against immorality. The standard historical explanation is that the Protestant Reformation frightened the papacy into reaction. The Protestants criticized the corruption of the Catholic Church, both financial and moral, as well as its doctrines. The papacy responded by clamping down on permissiveness, in an attempt to assert its moral authority. However, at precisely this time, syphilis exploded across the face of Europe. Much the same happened in China. During the Ming period (1368–1644), prostitution was originally widespread. No lethal venereal diseases were in circulation, and those who indulged in commercial sex washed scrupulously beforehand and afterward. Little social stigma was attached. The arrival of syphilis, beginning in 1505 in the Canton region, changed all this.

  When syphilis first struck Europe, its venereal nature was not evident. At first, it was viewed as divine retribution for general immorality, including gambling and neglect of religious duty, as well as sexual license. Only after a century or so did syphilis become a specifically venereal infection. By the eighteenth century, syphilis was known to be sexually transmitted, and contracting syphilis was seen as concrete evidence of infidelity or indulgence in vice. During this period, upper-class London families bribed the medical authorities to list relatives
who died of syphilis as tuberculosis victims. Consumption was fashionable, but the French pox was an improper way to die. By the early twentieth century, syphilis had become milder. Other venereal diseases were milder still, and sexual morals were starting to relax. The discovery of antibiotics and contraceptives resulted in further rapid loosening of sexual morals as the risks of both pregnancy and disease faded away. Then in the 1980s, AIDS emerged from Africa.

  Moral and religious responses to AIDS

  The puritanical reaction to AIDS has been relatively small in the industrial nations, especially when compared to issues such as smoking or abortion. AIDS affects only a small sector of society. Consequently, it is little threat to “respectable” people, as illustrated by Edwina Currie, U.K. Junior Health Minister, who in 1987 remarked, “Good Christian people … will not catch AIDS.”

  In Africa, AIDS is rampant throughout the whole population and threatens millions of lives. At the 1998 Anglican conference, the African bishops demanded that the church condemn homosexuality in accordance with the Bible. In contrast, most bishops from the United States, where AIDS threatens only a high-risk minority, want to portray themselves as “broad-minded” by condoning homosexuality. One bizarre result is that several African religious leaders have accused their politically correct Western colleagues of racism, on the grounds that they lack concern for the lives of poor blacks in Africa.

  Another consequence has been to promote the spread of Islam at the expense of Christianity. Moslem communities emphasize hygiene, prohibit alcohol (thus avoiding drunken lechery), and have stricter codes of sexual morality. Good Moslem people definitely will not catch AIDS. It is notable that in sub-Saharan Africa, the more northern nations, where Islam is strongest, have significantly lower incidences of HIV than those in the south, where Christianity is predominant.

  Nonetheless, Islam is now making major inroads into South Africa. Estimates of religious conversions show that between 1991 and 2004, Islam increased by more than five-fold. The suggested reasons are that Islam provides a response to the AIDS, alcoholism, and violence that are sadly too common in overcrowded black townships. It is in precisely these areas that the highest conversion rates occur.

  Public health and AIDS

  A common piece of disinformation is that AIDS patients pose no risk to the health of others. Because AIDS is not spread by casual contact, associating with HIV-positive individuals is risk-free. Rather, those who don’t have AIDS are a threat to those who do, because they pass on infections dangerous only to those with damaged immune systems. Although true, this is not the whole truth.

  Those infected with AIDS are a public health hazard, albeit minor. The risk is not from AIDS itself, but from associated infections. Some of the sporadic cases of tuberculosis in advanced nations trace back to visitors from Third World nations where TB is prevalent. The majority trace back to AIDS patients who have become a reservoir for tuberculosis in many major cities. Tuberculosis is mostly a hazard to children and old people. Allowing HIV-positive individuals to teach in school, under the guise of “human rights,” is a possible way to expose children to tuberculosis. Those with damaged immune systems also carry assorted other opportunistic infections, and prolonged treatment has resulted in many of these acquiring antibiotic resistance.

  Even today, some religious fundamentalists in America claim that God sent AIDS to punish society for the sin of tolerating homosexuality. Such small-town morality tends to drive homosexuals to the big cities. Conversely, many parents with young children have moved away from the inner cities, into suburbs or small towns. Such people tend to cite violence and drug addiction as the factors influencing their migration, because it is acceptable to object to these in public. Whether explicitly stated or not, such population movements also reduce the exposure of children to the tuberculosis and enteric diseases carried by HIV-positive persons. Whatever the reason, such migration does protect children from infection. Thus, from the 1980s until very recently, life expectancies have risen gradually in New York State (as in most advanced nations), while remaining constant or even falling in New York City.

  I am inclined to believe that many religious rituals and behavioral taboos functioned originally as pre-scientific public health. For example, incest, which is forbidden by most religions, increases the proportion of children born with genetic defects. Before the days of modern genetics, such taboos were justified by religious arguments. So why have most societies viewed homosexuality as taboo? Today a large proportion of homosexuals carry enteric diseases, including giardiasis and amebic dysentery, regardless of the presence of HIV. If enteric diseases were more prevalent among homosexuals in historical times also, homosexuality could have been a significant public health risk. Roughly half of infant mortality in modern Third World countries is the result of diarrheal diseases of one kind or another. Societies that tolerated widespread homosexuality might well have had more enteric disease, hence higher infant mortality. Perhaps this is one factor behind the religious taboos most societies have traditionally placed on homosexuality.

  Inherited resistance to AIDS

  HIV enters human cells in two steps. First, HIV must bind to its receptor, the CD4 protein, which is found on the surface of many cells of the human immune system. Next, the virus unfolds its docking protein to bind a “co-receptor.” Only after successfully attaching to the co-receptor can the virus actually enter the target cell. The most important co-receptor is the CCR5 protein.

  Although the CCR5 protein is part of the human immune system, it is not essential. About 20% of white people have a chunk of DNA deleted from one of their two copies of the CCR5 gene. Those with one defective copy of the CCR5 gene can catch AIDS, but its onset is slowed by several years. About 1% of white people have two defective copies of the CCR5 gene. These people are resistant to catching AIDS. This mutation is not found in Africans or Asians, suggesting that it is specific to Western Europeans.

  Variations in susceptibility to AIDS also derive from other changes in the CCR5 gene that alter the level of CCR5 protein expressed. An assortment of mutations in other genes also affects the progress of AIDS, although most of these are less important and less well understood.

  A rather tragic inverse example is also known, in which resistance to malaria increases susceptibility to AIDS. The Duffy receptor protein is found on the surface of red blood cells. Ninety percent of Africans possess genetic alterations that result in an absence of the Duffy protein. This provides resistance to some versions of malaria. However, it also increases susceptibility to HIV infection by perhaps 40%.

  The ancient history of venereal disease

  Sin, sickness, and sex are all inextricably intertwined in both the theory and practice of religion. Sin brings down divine punishment, originally most often in the form of sickness. Sex is often viewed as sinful, and certain religious groups regard even legal sexual relations between couples married in church with suspicion. Not surprisingly, religious enthusiasts view promiscuity and illicit sexual practices as bringing down the wrath of the gods and thus as responsible for a particular group of ailments: the venereal diseases. But which came first, the egg or the chicken? Did violation of pre-existing morality spread disease, or are moral codes actually public health measures constructed in response to the spread of venereal disease?

  The ancient religions of the Sumerians, Egyptians, Babylonians, Hittites, and others all had a series of male gods with relatively well-defined individual ranks and functions. There were also numerous goddesses, but these were far less individually distinct. Most female divinities had roles in fertility. Sometimes conception, childbirth, animal fertility, crop fertility, rainfall (or flooding of the Nile), and so forth were parceled out to separate goddesses, but often these functions overlapped and merged. Ancient fertility rites often included what today’s culture would regard as dissipated orgies of drunkenness and sexual indulgence. Associated with early fertility religions, we find an intriguing custom of sacred prostitution. Women s
acred to the fertility goddess made themselves available in exchange for contributions to the goddess’s shrine. This was viewed as service to the fertility goddess of their particular culture.

  Clearly, certain ancient views of sexual morality were quite different from ours. The current squabbles between those who disagree on issues such as abortion and homosexuality seem trivial compared to the gulf between the ancients and ourselves. Imagine the response from Americans who claim to respect “alternative lifestyles” if a Mormon or Moslem asked for polygamy to be tolerated. The ancients often accepted sexual profligacy without regarding it as an issue in itself. For example, adultery was not seen entirely as a sexual issue. Married women were forbidden sex with other men not merely because adultery was immoral, but because illegitimate children played havoc with codes of inheritance.

  The priestly moral code of the Bible comes later than many of the narrative accounts. The law was probably formulated by the priesthood during the later stages of the monarchy. However, many Bible stories show behavior that clearly violates these later, official standards but that was clearly regarded as acceptable by the people of the day. For example, the biblical story of Judah and Tamar includes sacred prostitution. This is viewed not merely as legal, but as morally acceptable by all the characters in this story. Thus, Judah, a respectable and prosperous farmer, openly sends a friend with payment for the sacred prostitute.