(FORTUNE Magazine) – At a trade show in Botswana, one of the most prosperous countries in Africa, a well-dressed crowd gathers to celebrate. The party, hosted by the De Beers-Botswana diamond monopoly, has attracted the nation's best and brightest: Miss Botswana Universe, business leaders, government ministers. They sip chardonnay and chatter with the aplomb of Manhattan socialites. In conversation, a television anchor calmly dismisses the extent of the AIDS epidemic in Botswana and disputes whether HIV even causes AIDS. Amid the good cheer, a jarring thought intrudes: Half the people in the room will probably be dead in five years.

The HIV/AIDS epidemic moving through Africa is unlike any plague the world has ever seen. It is bigger: More than 25 million Africans have already contracted the virus that will kill them within a decade; millions more will die in decades to come. It is crueler: Most epidemics decimate a population with frightening but merciful swiftness. This one travels in slow motion, hiding in its victims for years before they die slowly and painfully--but spreading all the while. And it is wreaking economic devastation in ways that epidemics rarely do, by attacking not the weak, the young, and the elderly, like most plagues, but killing off the most productive people in Africa: the well educated, the prosperous, the powerful, the parents of young children.

Although AIDS will claim many more victims than the medieval Black Death, which killed 20 million, Africa is in denial about the disease. Whole governments are struck dumb, unwilling to acknowledge the cause and extent of AIDS, and paralyzed by a lack of resources to fight it. The disease is strangely silent, almost underground. You don't see emaciated victims on city sidewalks in Botswana, South Africa, or Zambia. The people who return to their villages to die don't tell their families why they are sick. Wives don't admit that their husbands died of AIDS, and vice versa. Nurses at a small, tidy hospital near the gold mines west of Johannesburg say they have treated just 38 cases of AIDS among the 26,000 miners--even though miners have one of the highest HIV infection rates of any group in South Africa.

"Africa will never be the same," says Clem Sunter, an executive director of Anglo American, South Africa's gold and diamond mining colossus. "We don't know yet what the social and economic consequences will be, but AIDS will define the shape and structure of society in Africa. It is the biggest thing, bar none." Yet in South Africa, says Sunter, the silence on the subject is so great that "you can hear that proverbial pin drop."

AIDS lurks in rank back alleys and in plushly carpeted bedrooms; in thousands of grass-hut villages, where parents sell their last cow to raise money for a dying son or daughter; in hundreds of corporate boardrooms, like the one where eight of 12 top executives are HIV positive; in national parliaments, like Malawi's, where more than a dozen ministers have died; in the armies of Angola and Congo, where, according to the CIA, half the soldiers are HIV positive; in Lusaka, the capital of Zambia, where a TV ad promotes FUNERALS FOR YOUNG AND OLD!; in Uganda, where coffins with see-through portholes are pulled along the streets behind bicycles.

The statistics are stupefying. Africa, with just 11% of the world's population, is home to almost 75% of the people with AIDS. In Botswana, a Texas-sized country that borders South Africa, a United Nations report says 35% of men and women between 15 and 50 are HIV positive; if the infection continues to spread at its current rate, a 15-year-old Botswanan boy will have an 85% chance of dying of AIDS. South Africa, with by far the largest economy in Africa, has more HIV-positive people than any country in the world--about four million. (Except where noted, the statistics in this story are from the United Nations or the U.S. Agency for International Development--USAID).

Ironically, apartheid shielded South Africa from the epidemic. For years the country was isolated politically and economically by a global boycott protesting its treatment of blacks. When apartheid ended in 1991, South Africa's borders became more porous, trade with its neighbors resumed, and HIV exploded. Barely 1% of the country's adult population was infected ten years ago, vs. nearly 20% today. The economic boom that came with the end of apartheid is now in serious jeopardy. Other African countries, already among the world's poorest, are seeing AIDS devour modest gains in life expectancy and economic growth.

Not all of the continent is suffering. The disease is rare north of the Sahara, where less than 1% of the population is HIV positive. In Africa's western bulge, around Senegal and Liberia, only about 3% are infected. More conservative sexual practices in the mostly Muslim northern countries and a less contagious form of HIV in western Africa may explain the lower rates.

By contrast, in a broad swath south and east of Lake Victoria, the rates are hideously high (see map). The measure of devastation is not revealed in coarse economic statistics like GNP. The vast majority of Africans are subsistence farmers whose output doesn't even appear on macroeconomic radar. The GNP of countries with valuable natural resources isn't much affected by AIDS either. Botswana, with about two million people, has only 6,000 diamond workers. Nigeria, with 121 million residents, employs just 10,000 in the petroleum business. Because there are enough healthy workers to quickly replace those who fall ill, diamond and oil production don't slow down. Lack of rain or shifting prices of key commodities produce more dramatic shifts in economic activity than AIDS.

GNP statistics don't just fail to measure Africa's misery--they are beside the point. Although it sounds callous to say so, the world would hardly notice if Africa's entire economy disappeared overnight. Nigeria might be the exception; it provides 18% of the U.S.'s oil. Still, the combined economic output of the 45 sub-Saharan African countries, including South Africa, is about the same as Argentina's. Many African countries, despite populations of eight or ten million, produce about the same amount of goods and services as an American town of 60,000 people (see table). What little manufacturing there is--Africa accounts for a fraction of 1% of the world's manufactured goods--is mostly for local consumption. AIDS in Africa, in other words, won't make a blip in your retirement portfolio.

Where it should be making a very large dent but mostly isn't--because the developed world is inured to suffering in Africa--is in our collective conscience. AIDS is genocide by Mother Nature, and it is killing a continent. For millions of families, the devastation is immeasurable. Because HIV attacks the immune system, a victim typically develops a series of debilitating diseases before dying. A farmer's ability to work is diminished, of course, but so is the entire family's, as his wife, children, and relatives spend more time caring for him and less time tending crops. A study by a farmers union in Zimbabwe reported that maize production dropped 61% after the death of a breadwinner. Cotton and vegetable production fell by half. Families that grow more lucrative but labor-intensive crops to sell to cooperatives or along the roadside often must revert to subsistence farming when the male adults become sick.

Funeral expenses are large because the many friends and relatives obliged to attend must be fed. But the economic damage doesn't end with the funeral. Families desperate for a cure sell their most valuable assets to pay for treatment. The cattle go first, then the plow or the bicycle used to carry crops to market. "I know the family is on the brink of ruin when the bike or the plow get sold," says Jill Donahue, an American working to make small-scale credit available in Zambia. Even healthy farmers can be haunted by AIDS when their children move to cities to seek more opportunities, contract the virus, then return to their parents' village for care. "In Botswana, we go home to die," says Prisca Tembo, an AIDS prevention worker in the capital city of Gaborone.

In the course of impoverishing itself, a family frequently enriches people with virtually no modern medical skills. Traditional healers treat 70% of AIDS cases in Botswana. They charge $10 to $20 per visit to patients whose yearly income might be $500. For that they offer prayers and burn incense, or suggest that a victim cure his AIDS by having sex with a virgin. "If you want to get rich, come to Botswana as a traditional healer," says Karen Sorensen, a Lutheran missionary.

Benjamin Raletatsi runs an AIDS education center on the outskirts of Maun, a town of 35,000 in northern Botswana largely devoted to tourists viewing wildlife at the nearby Okavango Delta. Painted a cheery red, the center is near the riverbank, perhaps 500 dusty yards from the center of town, so visitors can come and go discreetly. Raletatsi says he urges AIDS victims returning to their villages to tell their families the disease is incurable, though he admits that most parents would ignore the disclosure. Robert Clay, a USAID health official who specializes in fighting AIDS in Zambia, saw this firsthand when a woman in his office got sick. "Her parents did everything to save her, even flew her to Harare [in Zimbabwe] for treatment," says Clay. "Her mother told me, 'I've already lost four sons to AIDS. I'm not going to lose my daughter.'" The daughter died too.

Every family with AIDS is miserable, but each family is miserable in its own way. Take, for example, a woman married to a prosperous man who dies of AIDS. Even if she manages to avoid catching the disease from her husband, she is subjected to family rituals that condemn her to poverty and make her vulnerable to the virus. The dead husband's brothers often claim his property--his home, his savings, his life insurance, even death benefits from his employer. Although some countries have outlawed property grabs, tribal customs can be too strong for widows to resist. A widow must be "cleansed" by her husband's brothers to avoid becoming an outcast. "Cleanse" is a cruel word, for it means having sex with the husband's brothers to wash away his spirit. The brothers may refuse to perform the cleansing until the widow hands over all her property.

Sometimes a widow is assigned to a brother and cared for as a spare wife, but not always. One of the saddest scenes in Africa is the women sitting by the roadside in Lusaka, pounding rocks with a hammer. They collect the rocks from a nearby field, then break them into coarse gravel. If they are fortunate, a contractor may come by and buy the gravel for a few cents, to mix with cement. Many of the women appear to be starving.

In families with young children, AIDS causes its own special problems and heartbreak. First, the father dies. A year or two later, the mother dies, having caught the virus from her spouse. They leave a handful of orphans who, maybe, can move in with grandparents. But the grandparents have often spent their savings on their dying son or daughter. At a time when they were counting on their children to support them in their old age, they instead have grandchildren to feed. Many such families face starvation. Even orphans taken in by relatives who can feed them have bleak futures. Zimbabwean orphans are half as likely to finish school as other children, mainly because their foster parents can't afford the minuscule school fees.

Africa's orphan problem is immense. The United Nations estimates that there are 13 million. David B. Dunn, the U.S. ambassador to Zambia, says that more than 25% of Zambia's children are orphans. The number is rising fast in the slums of South Africa. Driving through the rutted, narrow streets of Alexandra, a township on the outskirts of Johannesburg, health worker Linda Twala points out small hovels. "Six children in there. No parents. Four children in that one." Some youngsters eke out a living making trinkets to sell by the roadside, but often the girls become prostitutes, catching and spreading HIV, and the boys become petty criminals.

As a pediatrician in Zambia, Mutinta Nyumbu watched as AIDS invaded her country more than a decade ago. Now it has invaded her home. "I got a call yesterday from my cousin that another cousin had just had an AIDS-related stroke. He has eight children. I am already caring for my three sisters and their children. All their husbands have died of AIDS. How can I care for eight of my cousin's children? I just learned about this yesterday. I can't stop thinking about it." Other workers at her Lusaka health center have similar problems. "I've lost 20 relatives to AIDS," says Andrew Mlewa. "Now it's hitting my dad. He divorced my mom and married another woman. She died, her kids died. I have to drive eight hours to see him."

Certain sexual practices have hastened the spread of AIDS. African men often demand "dry sex," claiming that a dry vagina is more pleasurable. The women are forced to use herbs and other means to dry themselves, but dry sex results in vaginal tears and abrasions that increase the rate of HIV transmission. Most men in eastern and southern Africa are uncircumcised, which seems to make them more vulnerable to HIV. Africans also have high rates of untreated syphilis, gonorrhea, and other sexually transmitted diseases, increasing by 20-fold their chances of catching HIV.

Condom use is rare; a Zambian survey found that only 6% of people reported using a condom in their last encounter with a spouse or live-in partner. Nils Gade, head of the Society for Family Health, a nonprofit organization in Zambia that distributes condoms, says Africans know, intellectually, that unprotected sex leads to AIDS. "If you quiz them on it, 95% of their answers are correct," says Gade. "But their behaviors don't change. It's like talking to teenagers about smoking. They know it kills, but they do it anyway." Gade says attitudes are changing, but slowly. "Ten years ago when our workers went into bars and tried to distribute condoms, they got thrown out. People would say there was no such thing as AIDS. Now they know."

Many men take young girls as partners, assuming they are less likely to have the virus than older, more sexually active women. Other men believe they will cure their own HIV by having sex with 100 virgins; they claim the virus is passed on to the girls. A survey of 1,600 children in Lusaka found that 25% of 10-year-old girls in poor sections of town had had sex, and 60% of 16-year-old girls. In countries where sex with young girls is most prevalent--Zambia, Botswana, Zimbabwe--overall rates of HIV are far higher.

Well-educated, well-paid men are at particularly high risk for AIDS. They can afford to give clothes and a cell phone to a girlfriend in exchange for sex, to pay a prostitute, or to set up a mistress in an apartment. Men in authority can often demand sex from powerless underlings. The AIDS rate among schoolteachers, who are mostly male, is astoundingly high. About 85% of the teachers who died during the past few years in the Central African Republic were HIV positive. The reasons aren't entirely clear, but it appears that many demand sex from the children or their mothers in lieu of fees. Because women tend to be less educated than men and much less likely to have a job, it doesn't take much wealth to buy or barter for sex. A South African truck driver making $400 a month is rich to local women who don't earn that much in a year. Men from Mozambique and Tanzania leave their families to work in South African mines. Bored, lonely, and well paid, they spend their money on prostitutes.

Educated women appear to be just as much at risk as their male counterparts. They, too, are mobile and can travel and party in ways poor rural women cannot. "This is a very materialistic society," says a black American woman who has worked in Johannesburg for many years. "Two men I know were told by their girlfriends that their cars weren't good enough, that if the men didn't get new cars, they would leave." In Zambia, educated women past their teens are three times more likely to contract HIV than uneducated ones.

No society can afford to lose its best and brightest, least of all African countries that have yet to recover from a century of colonialism that excluded virtually all blacks from higher education and managerial positions. When Rwanda won independence from Belgium in 1962, it had one African high school graduate. Congo had five black college graduates at independence. Many African countries pursued Soviet-style socialism for decades after independence, with disastrous economic results, but schools, at least, began to improve. When some governments finally began privatizing utilities, mines, and factories in the 1980s, a new generation of managers began mastering the intricacies and terrors of capitalism. After decades of economic decline, the growth rate in southern Africa nudged up to 4.5% a year in the early 1990s.

Now the homegrown managerial talent Africa so desperately needs is being decimated. The prevalence of HIV among skilled and highly skilled workers in South Africa is predicted to peak at 23% and 13%, respectively, in five years. That is below the rate for miners, 29% of whom are expected to be HIV positive by 2005. Like all epidemics, AIDS in Africa will eventually run its course. Unlike measles or smallpox, HIV is relatively hard to catch. As fewer people engage in risky sexual behaviors, the infection rate will stabilize and eventually decline.

Until that happens, the impact on companies will be considerable. Kristina Quattek, an economist in Johannesburg for the British brokerage ING Barings, says that while just 9% of people in South Africa's finance and insurance industries are estimated to have AIDS, "99% of them are skilled or highly skilled." In city after city, executives tell of hiring two or three trainees for each new managerial job in anticipation of attrition from AIDS. In Zambia, corporate expatriates who come for a year or two to train executives find their plans to return home thwarted. "We've had people set to leave, then they discover that the people they trained are dying of AIDS," says Margaret Mwanakatwe, who until recently ran the Zambia Investment Center in Lusaka and is now head of the Barclays Bank there. "Sometimes they stay, but sometimes the government won't extend their visas because it wants Zambian citizens to fill those jobs. So the expat leaves, and the company struggles."

A large, foreign-owned copper-products company in Zambia offered to provide life insurance for its dozen or so senior managers. None would take the HIV test the insurance company required, says a company consultant. The foreign owners have increased their investment, but they will probably have to bring in expatriates to run the plant. "That's not something we wanted to do," says the consultant. "We wanted to hire and train local people."

Roseanna Price, president of Mars International, an HMO-like firm in Zambia, studied the potential impact of AIDS on several Zambian industries for a doctoral thesis. She says the electric-power sector is likely to get clobbered. Eight of 12 top executives at one power company are HIV positive, she learned. The crews that maintain power lines and equipment are also becoming less efficient, as skilled workers take time off to attend funerals or get sick and die themselves.

Other observers in Zambia say AIDS has diminished railroad track crews--the last thing a landlocked country, already hampered by the high cost of getting goods to markets, can afford. A large Lusaka bank is ailing because so many of its loan officers have become ill. "The bank does all the right things," says Price. "It offers all kinds of benefits and treatment. It knows sick people are walking around the office, but it doesn't know how to get them to treatment." The employees, afraid that co-workers will learn of their illness, won't visit the bank's HIV centers.

It is difficult to calculate the full damage AIDS will wreak on Africa's formal economies, because companies themselves don't have a good grasp of the problem. Lisa Cook, deputy director of the Center for International Development at Harvard, says the center did a survey of 2,000 companies in 20 African countries and got wildly inconsistent answers. "It was hard for companies to even know how to answer. AIDS masquerades as so many different diseases. Their workers leave, and no one knows exactly why." Many companies apparently don't want to know what lies ahead. "People are burying their heads," says Gillian Nur Samuels, who led a study for Metropolitan Life, an independent South African insurance company. "Most companies feel it won't impact them. They are trying to ignore it."

It seems almost forgivable--sometimes--that people avert their eyes from such crushing problems. Even if no other African caught HIV again--which is inconceivable--the plague would continue to kill for a decade or more. In the absence of treatment to stop or delay the onset of symptoms, that's how long it takes for a victim's immune system to be destroyed and for AIDS to begin. (See following story for an update on the newest AIDS vaccine.) The infection rate in many countries is continuing to rise; 3.7 million more Africans became infected last year, 22% more than in 1995.

Kristina Quattek, the Barings economist in Johannesburg, was near tears as she talked about what might have been in South Africa. "There were such great prospects for investment and trade after apartheid ended," she says. "Mandela was President, and we were avoiding overt racial tension. The country had everything going for it. We had a well-developed financial section, and the government was doing all the right things on macroeconomics and trade. We hoped that foreign investment would flow. That hasn't happened. It seems so unfair."

The governments of some of the countries most affected by AIDS have been alarmingly inert, even counterproductive, in attacking the problem. By far the worst offender is Thabo Mbeki, President of South Africa. He claims to have personally investigated the disease and doubts that HIV leads to AIDS. He questions whether AZT, one of the most useful medicines in slowing the progress of HIV, really works. (Nelson Mandela spoke out only once about the disease while he was President.) Partly as a result of Mbeki's foolishness, South Africa refuses to give AZT to pregnant women close to term--even though it greatly reduces the spread of HIV to newborns. Dr. Colin Eisenstein, medical director at Anglo Gold, the nation's biggest gold-mining company, is furious. "If there were a foreign army camped out on our border that we knew was going to kill 25 million people, we'd do something about it," he says.

In other African countries, civil servants work to educate people about AIDS, but top leaders are invisible, rarely speaking out in public and failing to convey a sense of urgency. Only in Uganda, perhaps the hardest-hit country in the world, has the President, Yoweri Musevini, led the charge. The prevalence of HIV in Uganda has actually declined over the past 20 years, from 15% to 8%. Miss Botswana Universe, Mpule Kwelagobe, is crusading against AIDS in her country. In Zambia, where government workers, foreign charitable organizations, and groups like the U.S. Agency for International Development have worked hard, there are signs of progress. In areas of Lusaka, the HIV rate among 15- to 19-year-olds has dropped sharply. Robert Clay, the USAID employee, says it's not clear whether rates will stay down as the youngsters become more sexually active, "but it's a beginning."

Perhaps the safest place to be in southern Africa is at a large, foreign-owned company. After Ford flew in officials from the Centers for Disease Control and Prevention to educate local executives, its plant in Pretoria, South Africa, shut down operations and assembled everyone on the factory floor for a day of seminars, a speech from the local CEO, and dramas on AIDS. John Strydom, Ford's medical director in Pretoria, installed condom dispensers and plastered walls with laminated posters proclaiming Ford's obligations to HIV-positive workers. He has brought in employees' wives to teach them about prevention and is now planning to invite their teenage children. Strydom, a burly Scot with a thick brogue, says he is hopeful that the HIV rate among Ford's workers will stay below the national average. Most live with their families and walk to work, which may enable them to avoid the temptations that befall so many itinerant Africans. He admits, though, that he doesn't know what's in store. "We just hired 300 new workers. What percent of them are HIV positive? How many will be dead in two or five years? I just don't know."

AIDS in Africa presents the rest of the world with a complicated, maddening dilemma. How do compassionate people even begin to help? Whom should they help first? The terminally ill suffering from painful AIDS-related infections? Orphans who face a life of Dickensian bleakness? Healthy people who need to be educated about how to avoid contracting the virus in the first place? Or should the U.S. and other rich countries allocate money to provide the expensive medicines, widely available in the West, that can delay the onset of symptoms for years?

Here's another question: Would any of it make a difference? The billions of dollars wealthy nations have spent on roads and dams and malaria eradication haven't changed the lot of the average African. If African men refuse to use condoms and continue to view women as nothing more than sexual objects, how much sympathy do they deserve? Or are they just as insensitive as men everywhere--and unlucky enough to have been born in a place where 100 variables have conspired to make AIDS so ruinous?

No large-scale solution to AIDS in Africa is possible until the continent's leaders acknowledge their plague and cheap medicine becomes widely available to fight it. In the meantime, there are some things ordinary people can do. Persuade your church to bankroll a village orphanage. Help young girls buy school uniforms and books so that they can attend class. Contribute to an organization that sends medical supplies to nursing stations. Travel to Africa; it needs the tourist dollars. After you've oohed and aahed at the wild animals, visit a U.S. embassy to ask which private and government agencies deserve help.

No matter what well-intentioned people do, the suffering in Africa will linger for decades. AIDS will not come close to killing everyone there, of course, but it is certain to prove more devastating than any epidemic in history. It's as mind-boggling as it is heart-wrenching that as the developed world races over the Internet into the third millennium, Africa is falling ever deeper into poverty and death from a pestilence right out of the Old Testament.

FEEDBACK: boreilly@fortunemail.com