The First American Ebola Outbreak

In the spring of 1983, a flock of wild ducks carrying a strain of avian influenza virus settled on a pond in a chicken farm in eastern Pennsylvania. The virus was excreted in the ducks' feces, which meant that it got onto the ground and then onto the boots of a farmer, which is why in turn it soon found its way into the chicken barn. From there the virus spread, carried by truckers who go from farm to farm collecting eggs, selling feed or taking broilers to market. As it spread, it replicated hundreds of millions of times, and as it replicated it underwent a critical mutation that turned it from a relatively benign virus into a killer. By late spring, chickens were collapsing within days of infection. By October, 17 million domestic birds—broilers, layers, turkeys, guinea fowl—from Pennsylvania down through Maryland and Virginia were dead.

The great Pennsylvania chicken epidemic went largely unnoticed at the time. In 1983, people did not draw analogies between the health of domestic fowl and the health of the general public. But today is a different matter. The United States is in the grip of paranoia about viruses and diseases and what happened in Pennsylvania has acquired a certain symbolism. In the past six months alone, there has been a Hollywood film, a made-for-TV-movie, a cover story in Newsweek and countless news specials and media reports on the subject of killer viruses. This spring a small outbreak of the African Ebola virus in Zaire drew virtually every major news organization to the hitherto unknown city of Kikwit. Richard Preston's The Hot Zone, a terrifying tale of how close America came to a major epidemic of the Ebola virus in 1989, has been on The New York Times best-seller list for thirty-seven weeks. And a well-received tome about infectious disease has also arrived from Laurie Garrett, a science reporter for Newsday, which is filled with gloomy quotations like this one, from the Nobel Prize-winning biologist Joshua Lederberg: "Are we better off than we were a century ago? In most respects we are worse off. We have been neglectful of the microbes and that is a recurring theme that is coming back to haunt us."

In all of these books, movies and news reports there is a sense of fear: Americans have been well and properly frightened of viruses, after all, since the AIDS epidemic began fifteen years ago. But there is also a sense of helplessness, a feeling of fatedness, as if we are all somehow in the same position today as the chickens of the Northeast were twelve years ago. "The chicken population in Pennsylvania [in 1983] is like the world as it is in this moment," Robert G. Webster, one of the country's leading virologists, recently observed. "What would we have done if this virus had occurred in humans? There are millions of us 'chickens' just waiting to be infected."

What are the sources of this pessimism? A generation ago, American public health officials were talking openly about the impending end of all infectious disease. Anti-biotics had been developed. Polio had been conquered; and, in one of history's greatest medical triumphs, smallpox was eradicated. Whatever apocalyptic fantasies existed at the time were, by today's standards, tame. Consider the movies. Panic in the Streets, Elia Kazan's Oscar-winning film of 1950, has essentially the same plot as "Outbreak," this spring's big medical thriller: A deadly infectious disease has entered the United States from abroad and is threatening to sweep across the country. In Kazan's movie, however, the plague is contained by one man, a local public officer. In the new movie, it takes several divisions of the U.S. Army. In Panic in the Streets, three people die. In "Outbreak," hundreds die. Most importantly, perhaps, the virus in "Outbreak" is stopped only when, in a stroke of pure luck, a cure is found; but in Kazan's film a cure for the plague exists all along. In fact, in the older film the prospect of the plague spreading across the country appears to be terrifying not because it threatens the lives of countless Americans, but because it would require a costly and presumably difficult mass-inoculation program. Despite the similarities in their plots, the two films have about as much in common as "Marcus Welby, M.D." has with "E.R."

Some of the blame for this transformation clearly belongs with AIDS, the epidemic that has more or less shattered the public's confidence in the power of science. But AIDS has never been seen as a threat to the entire species. In fact, AIDS is exactly the opposite of the kind of random, uncontrollable epidemic that seems to have now seized the popular imagination. The truth is that it is very hard to find an adequate explanation for the current American obsession. Joshua Lederberg's comment that we are worse off today than a century ago is proof only that he is a better student of microbiology than of history.

How can we be worse off than we were at a time when the average American lived only into his 40s, and the hospitals were filled with concurrent epidemics of tuberculosis, acute rheumatic fever, smallpox, diphtheria, tetanus, polio and pneumonia? Ebola may be new and scary, but in the twenty years since its discovery it has killed no more than several hundred people. In fact, it is safe to say that more Zairians in Kikwit died of diarrhea this spring than of Ebola. Even the analogy to the Pennsylvania chickens, though it fits the current hysteria like a glove, is absurd. Human beings do not live their lives crammed next to each other in metal cages. They do not wallow in their own feces. They have the brains and the ability to take precautions against disease and contagion. People are not chickens. So why all of a sudden are we convinced that we are?

II.

African Ebola is one of the deadliest of known human viruses. It kills by clotting the blood of its victims, shutting off the flow of nutrients to key parts of the body and chewing through connective tissue, so that the infected literally cough their guts out. No one knows what animal serves as Ebola's natural host, but it can jump from species to species, from guinea pigs to humans, killing virtually everything it touches. There is no cure for Ebola. And there is no vaccine. On the three occasions that it has broken out among humans—twice in Zaire and once in the Sudan—it has left behind a trail of death. Only once has Ebola made its way to North America and that occasion is the basis of Richard Preston's The Hot Zone.

It is a remarkable book, rivetingly written. When a shorter version of the manuscript appeared in The New Yorker several years ago, it provoked a bidding war in Hollywood, and since its publication as a book late last year, it has remained at or near the top of best-seller lists. It is safe to say that it is because of the success of The Hot Zone that "Outbreak" was made, that the Ebola outbreak in Zaire was covered as feverishly as it was, that the idea of killer viruses has achieved such sudden prominence. In the epidemic of virus paranoia, The Hot Zone is patient zero.

Preston's book centers on a shipment of monkeys brought in 1989 to a quarantine facility in Reston, Virginia. Not long after their arrival, the animals began to get sick. Mucus streamed from their noses. Their lungs became clotted and collapsed. Their intestines turned the consistency of gumbo. As one animal after another died, the keepers of the monkey house were first puzzled, then terrified as they realized that they had on their hands the first North American outbreak of African Ebola virus. To make matters worse, the strain of Ebola in the monkey house appeared to be different than most. African Ebola passes from one victim to another through direct contact with blood or bodily fluids. But Ebola Reston, as it became known, appeared to be airborne, moving from one monkey to another as if it were the flu.

The gravity of this situation cannot be exaggerated. By the time the U.S. Army and the Centers for Disease Control were notified, several workers in the monkey house in Reston had already clearly been exposed to the infected monkeys. They had also gone home to their families and eaten in restaurants and ridden on buses, which meant that the virus, if it was truly was airborne, might have spread throughout the Washington area. Acting under strict secrecy, so as not to cause public alarm, the Army moved in and sealed off the monkey house, incinerating every animal inside. Then they braced for a possible human epidemic. It never came. By some genetic fluke, the same mutation that rendered Ebola Reston airborne apparently also left it harmless to humans.

If this plot sounds familiar, it should. It is essentially a beefed-up version of The Andromeda Strain, Michael Crichton's 1969 best-seller. (Such is the lingering impact of Crichton's novel, and of fiction upon fact, that in both The Hot Zone and The Coming Plague scientists are quoted as using the book's title to refer to the hypothetical virus capable of wiping out humanity.) In Crichton's book, the American military sends up a secret satellite that disrupts the delicate ecosystem of a strange and hostile place (outer space) and comes back down with a microbe that kills everyone it touches (the Andromeda Strain). A team of crack scientists put on space suits and seal off the town invaded by Andromeda. The microbe, they soon realize, is airborne and threatens the United States. Just as it is clear that it has escaped, however, the microbe mutates and in its new form ends up harmless to humans.

But the parallels go beyond plot. Both books, Crichton's work of fiction and Preston's work of non-fiction, have the same cinematic breathlessness, the same quick cutting between scenes, the same hushed melodramatic endings to paragraphs, the same heroic depictions of scientists. Crichton gives his chapters titles such as "Contact," "Crisis," "Alert," "Decontamination," "Spread," "Evaluation," "Analysis," "Level 5." Preston gives his chapters titles such as "Diagnosis," "Total Immersion," "Into Level Three," "Exposure," "Chain of Command," "Insertion," "Inside," "Decon." Of course, The Hot Zone is a true story and The Andromeda Strain is not. But there are conventions of fear in modern American culture, and there is no denying The Hot Zone is written, in style and substance, in self-conscious imitation of a sci-fi thriller. This is one of the things that makes the book so exciting. It is also what makes the book occasionally dishonest.

Preston's book begins, for example, in a place called Kitum Cave at the base of Mount Elgon on the Kenyan-Ugandan border, a huge volcanic cavern that for centuries has served as a gathering place for the wildlife of the rainforest. "Kitum Cave is Mount Elgon's equivalent of the Times Square subway station," Preston writes. "It is an underground traffic zone, a biological mixing point where different species of animals and insects cross one another's paths in an enclosed air space." Since two of the known cases of Marburg virus, a close cousin of Ebola, were found in people who had visited Kitum, Preston treats the cave as the birthplace of Ebola. In the book's climactic scene, he actually dons a plastic biohazard suit and visits the cave himself, gingerly making his way along the cavern's walls.

In Medieval times, the plague was thought to originate in miasma, or a marshy putrescense, and Kitum Cave is Preston's miasma, a dark hole deep in the rainforest that gives Ebola an appropriately sinister provenance. It is a marvelous image. Just what it has to do with the story, beyond the adding of atmosphere, is a little unclear. Two of the three known outbreaks of Ebola took place hundreds of miles away from Kitum in Zaire, and the third outbreak was centered in the grasslands of southern Sudan, which suggests that there may be no special relationship between Ebola and the rainforest at all.

Preston also follows the conventions of the genre in his over-the-top descriptions of the men who hunt down and probe the mysteries of Ebola. They are blunt, passionate and iconoclastic: loners driven by a fierce desire to know the truth. "C.J. Peters," he writes of one,

Could swim through bureaucracy like a shark. He inspired great loyalty in his staff, and he made enemies easily and deliberately, when it suited him. ... He was required by Army regulations to show up for work at eight o'clock in the morning, but he usually drifted in around ten o'clock. He disliked wearing a uniform. Usually he wore faded blue jeans with a flaming Hawaiian shirt. ...

(The Roy Scheider role.)

On another occasion, our breathless correspondent catches up with the co-discoverer of Ebola, Karl Johnson, "a lean, bearded man, with a soft voice that one had to listen for in the wind" (the Sam Waterston role). He is fly-fishing on the Bighorn River in Montana, where Preston poses the overwhelming question:

"Are you worried about a species-threatening event?"

He stared at me. "What the hell do you mean by that?"

"I mean a virus that wipes us out."

"Well, I think it could happen. Certainly it hasn't happened yet. I'm not worried. More likely it would be a virus that reduces us by 90 percent."

"Nine out of ten humans killed? And you're not bothered."

A look of mysterious amusement crossed his face. "A virus can be useful to a species by thinning it out," he said.

One wonders, reading this passage, just who is manipulating whom. Is Johnson slyly putting one over on the naive journalist about just how nonchalantly he views the "thinning" of the species? Or is Preston complicit in all of this, and trying to scare the bejesus out of his readers? Either way, it would have been nice if Preston had shown even a trace of skepticism about the pronouncements of his lean, grizzled hero.

The people who worry about epidemics, after all, are people inclined to think in apocalyptic terms. They spend all their time looking at or thinking about things that kill people and then trying to talk non-medical people into what often seems like an overreaction. The best of them, like those who shut down the San Francisco bath houses in the early 1980s, can accurately see the possibility of disaster with only the scantest of evidence. But it is important to realize that the alarmism that makes them good at their job also makes them rather unreliable on matters such as the future of the human race. I remember once having lunch with a well-known epidemiologist, a man who had cut his teeth investigating outbreaks of food poisoning. We were supposed to be talking about the AIDS epidemic. But in the course of our meal he became increasingly distracted, staring worriedly over my shoulder. Only at the end of our lunch did I figure out why. Behind me was the restaurant's salad bar, and behind that a large picture window. For a full hour he had been fixated on the sun creeping slowly along the restaurant floor, menacingly making its way toward the potato salad.

III.

Still, it would be a mistake to dismiss The Hot Zone as frivolous. This is more than merely a thriller. What makes the book so interesting, and helps to account for its extraordinary popularity, is the manner in which Preston manages to turn the story of Ebola into an ecological parable. This is not only a medical warning, it is also an environmental warning. In Preston's hands, epidemiology leads directly to a kind of Luddism. For the new killer viruses of the African rainforest, he believes, represent nature's response to humanity's environmental crimes.

This is an argument that rose to prominence with the emergence of AIDS. HIV, the theory goes, probably lived for millennia in the jungles of Africa, peacefully co-existing with its natural animal host. From time to time, it may have jumped into humans, making a brief run, say, through a jungle village, but it stayed in the rainforest. Then came the massive environmental upheaval of the 1970s. Truck routes were built into the continental interior. The Ugandan-Tanzanian war, which took place at the center of where monkey-borne HIV is thought to reside, uprooted entire populations. Cities began to spill over into what had been virgin territory, bringing with them new patterns of sexual behavior and prostitution. The effect was to give HIV a clear route out of the jungle. And what happened with AIDS, Preston says, is what is now happening with Ebola, and may soon happen again with something infinitely nastier than either of them.

Laurie Garrett takes this argument one step further. In The Coming Plague, her 750-page opus, she is not concerned just with rainforest viruses. She maintains that toxic shock syndrome, Legionnaires' disease, the rise of antibiotic-resistant infections, Lassa fever, Hantaan virus and virtually every other microbial outbreak of the past twenty years are all linked by the same pattern of environmental irresponsibility. "Ultimately humanity will have to change its perspective on its place in Earth's ecology if the species hopes to stave off or survive the next plague," she concludes. In the world of microbes,

Human beings stomp about with swagger, elbowing their way without concern into one ecosphere after another. The human race seems equally complacent about blazing a path into a rainforest with bulldozers and arson or using an antibiotic "scorched earth" policy to chase unwanted microbes across the duodenum.

This idea clearly has its roots in the environmentalism of the 1980s. Then we were told that destroying the rainforest would irreparably alter our climate. Now we are told that it will destroy our health. This revision, however, is not trivial. If the environmentalist warnings failed to ignite mass fear or mass politics, it was because they were so abstract. For how long could a series of speculative scientific projections about long-term trends toward warmer weather (of all the terrifying fates!) hold the public's attention? But the new virus paranoia puts the old global warming paranoia to shame. This is not a prediction. It is a judgment. We have wronged nature and it will exact its revenge.

Just listen to the wrathful Preston, in the final chapter of his book:

The emergence of AIDS, Ebola and any number of other rainforest agents appears to be a natural consequence of the ruin of the tropical biosphere. The emerging viruses are surfacing from ecologically damaged parts of the earth. ... In a sense, the earth is mounting an immune response against the human species. It is beginning to react to the human parasite, the flooding infection of people, the dead spots of concrete all over the planet, the cancerous rot-outs in Europe, Japan and the United States, thick with replicating primates, the colonies enlarging and spreading and threatening to shock the biosphere with mass extinctions. Nature has interesting ways of balancing itself. The rainforest has its own defenses. The earth's immune system, so to speak, has recognized the presence of the human species and is starting to kick back in. The earth is attempting to rid itself of an infection by the human parasite. Perhaps AIDS is the first step in a natural process of clearance.

There is a very peculiar collection of ideas here. The ideology expressed is not at all like the one in The Hot Zone's fictional predecessors from the cold war. They shared Preston's preoccupation with mankind's extinction, but without this self-loathing. Crichton's book delivered only a straightforward warning that America has enemies even in the farthest of places (outer space) and the smallest of sizes (sub-microscopic). And in "Panic in the Streets" the plague is carried into the United States by an illegal alien. The evil isn't American, it's someone else's.

But Preston's notion of plague isn't really biblical either. True, it has a hoary punitive dimension: The idea of disease as a punishment for wickedness. And so does Outbreak, in which the killer virus comes into this country as a result of a Pentagon biological warfare experiment gone awry. "This is what happens when men go chopping down trees where no man should be," an ancient African medicine man says as he surveys the ruins of a village destroyed by the virus at the beginning of the movie. "The Gods got angry. This is a punishment." In the Bible, however, natural apocalypse is banished, in a climactic moment in Genesis, from the scheme of reward and punishment. God promised Noah after the great flood that he will never again "destroy every living creature," and created the rainbow to attest to the promise. And so plague was not apocalypse. Plagues in medieval times were "visitations." The choice of words was deliberate: They came and they left. And AIDS is "the gay plague" to the Christian right precisely because it seems so selective: It singles out those guilty of the sins of homosexual promiscuity and drug use.

Today's imagined plague is something entirely new. We are in the grip of a terrifying super-virus of our own creation, a mutant hybrid of cold war apocalyptics, biblical moralism and environmental fire and brimstone. Is it any wonder that grown men are running around comparing mankind to chickens?

IV.

What should we make of all this? Is nature really about to teach humanity a lesson? The answer depends in large part on whether you are an optimist or a pessimist, and on the magnitude of your faith in the power of medical science to respond quickly to new problems. But it should be said, first of all, that nature has been striking back against the ceaseless explorations and expansions of human beings, against the "human parasite," for as long as men have roamed the earth.

In Plagues and Peoples, which appeared in 1977, William McNeill pointed out that the full development of central and southern China was probably delayed for five or six centuries by the "disease barrier" that the Yangtze River and the warmer climate of the south created. The effort to explore and to civilize the New World probably brought syphilis back to Europe, where it raged as the AIDS of its time throughout the sixteenth century; and typhus came to Europe at the end of the fifteenth century when Spanish soldiers picked up the infection fighting in Cyprus. That HIV and its kin should have been loosed from the rainforest by the environmental disruptions of the past twenty years, in other words, is hardly unprecedented. When it comes to "remodeling" natural environments, McNeill writes, man has been very good at dealing with what can be seen and can be manipulated. But there are things that cannot be seen and cannot be manipulated, and

human intelligence remained for thousands of years only fumblingly effective in dealing with disease-causing micro-organisms. As a result the ravages of disease among crops, herds and peoples played a significant part in human affairs throughout historic time.

McNeill's point, however, is that while man's efforts to "remodel" his environment are sometimes a source of new disease, they are seldom a source of serious epidemic disease. Quite the opposite. As humans and new microorganisms interact, they begin to accommodate each other. Human populations slowly build up resistance to circulating infections. What were once virulent infections, such as syphilis, become attenuated. Over time, diseases of adults, such as measles and chicken pox, become limited to children, whose immune systems are still naive. McNeill remarks that it was during the mid-fifteenth century that the population of Europe began to expand steadily, even though "it was during these decades that the oceanic discoveries took place, and European sailors had the opportunity to import new infections into their homelands from the ports of all the earth." Precisely because they had been exposed to these micro-organisms, the Europeans were hardened to their effects.

This, says McNeill, is the paradox of infection: "The more diseased a community, the less destructive its epidemics become." Who, after all, suffered the most from the discovery of the New World? Not the conquerors, the ones who were despoiling a virgin environment. It was the conquered, the American Indians, the peoples living on a secluded and pristine continent, who were all but wiped out by the sudden arrival of smallpox. This does not mean, of course, that we should not worry about the effects of man's continuing assault on nature. But it does mean that there is nothing inherently terrifying about the fact that the West is now being exposed to new microbes from equatorial Africa. We are ultimately safer in a world where new viruses and bacteria are in constant circulation, and where human populations can encounter and build defenses against them. Unlocking the viruses of the rainforest is part of the way we tame nature, not the way nature tames us.

One can go further. Sometimes disrupting the environment is the way we get rid of disease. In England in the seventeenth century, for example, farmers began disrupting nature by raising livestock on a large scale for the first time. What happened? Malaria-carrying mosquitoes, which used to feed on people, switched to cattle. And since cattle aren't an hospitable host for the malarial plasmodium, the disease, which had been endemic in Britain for centuries, retreated from the British Isles for good. Or consider Russia in the eighteenth century, when the natural ecosystem of the countryside began to be disrupted by the aggressive expansion of agriculture into areas that had previously been wilderness. The plowing of fallow land destroyed the natural habitat of the rats that carried the bubonic plague. Thus freed of plague, which had been a persistent problem in Russia long after the disease left the rest of Europe, the Russian population grew from 12.5 million in 1724 to 21 million by the end of the eighteenth century.

The point is that the relationship between environment and disease is a complicated one. There are diseases that are caused by environmental disruption, diseases that are eliminated by environmental disruption and diseases whose rise has nothing to do with environmental disruption. The current plague paranoia is an obsession with the first category. Thus Garrett is very convincing when she talks about how the new cities of the Third World—overpopulated, vastly underserved by medical care, troubled by appalling sanitary conditions—are breeding grounds for new infections. But this is not an accurate diagnosis of all new diseases.

Garrett, for example, writes a long and intelligent chapter on the worrying rise of new bacterial strains that are resistant to the antibiotics that once cured them easily. But what does this have to do with mankind's environmental responsibility? Antibiotic resistance is the result of shoddy infection control procedures in hospitals, well-meaning but ill-advised overprescription of certain drugs by physicians and the fact that the pharmaceutical industry got cocky in the late 1980s and stopped developing new classes of antibiotics. We could preserve every acre of rainforest the world over, clean up every river and stop every war, and we would still have a raging antibiotic resistance problem.

Even in cases where environmental disruptions do seem to have played a role in the emergence of disease, it is not the overwhelming factor that Preston and Garrett imply. HIV may have been loosed from the jungle by the upheaval in Africa during the 1970s. Still, absent epidemic levels of unsafe promiscuous sex and intravenous needle use in the West, the virus would have gone nowhere. The critical factor with AIDS, and with an awful lot of the diseases that we face, is what we do to ourselves and each other, not what we do to our environment.

But these are, to some extent, side issues. There is no question that for whatever reason, as a result of what man does to himself or what he does to his environment, the threat of infectious disease is on the rise in the world right now. The re-emergence of tuberculosis and untreatable strains of malaria, for example, are worrisome trends. Should we be scared? Well, yes and no. In his brilliant study, Evolution of Infectious Disease, Paul Ewald describes how the chaos at the end of the First World War directly contributed to the rise of an unusually vicious strain of influenza. The result was the influenza pandemic of 1918, which left 20 million people dead. This could happen again. But whether or not some new virus could emerge that could wipe us all out is an entirely different matter. It is simply very difficult to imagine where such a super-virus would come from or what it would look like.

Let's start with Ebola. Preston argues that Ebola, under the right conditions, could obliterate a significant chunk of humanity. "If the Ebola Sudan virus had managed to spread out of central Africa," he writes of one of the first known Ebola outbreaks, "it might have entered Khartoum in a few weeks, penetrated Cairo a few weeks after that, and from there it would have hopped to Athens, New York, Paris, London, Singapore—it would have gone everywhere on the planet. Yet that never happened. ... For reasons that are not clear, the outbreak subsided."

But this is simply not true. The reason for the abatement of the outbreak is entirely clear. Ebola kills its victims too quickly. It is one of the fundamental rules of infectious diseases, which Preston no more than hints at, that the deadlier they are to the people they infect, the less dangerous they are to everyone else. Ebola kills within two weeks, and during those two weeks it is not as if its victims are walking around meeting and infecting hundreds of unsuspecting others the way someone with a cold does. After only a brief incubation period, they are at home or in the hospital, immediately, obviously and unambiguously sick, with limited contact with the outside world. How much chance, then, do they have to pass on their disease?

This is why Ebola causes outbreaks, not epidemics. It cannot sustain itself. Ironically, the outbreak in Zaire that has so clearly boosted the visibility and the sales of The Hot Zone is also the event that most emphatically demonstrates the book's dishonesty on this point. Here was a crowded, filthy slum, crammed with 500,000 people under the worst sanitary conditions: an ideal breeding ground, in short, for an epidemic. And how far did Ebola get? Two hundred people. Maybe a few dozen more. Ebola Sudan was as likely to get to the moon as it was (in Preston's hyperbolic formulation) to leave Central Africa and find its way to Athens, Paris, London and Singapore.

An airborne version of Ebola, of course, is a different matter. Had the Reston strain of Ebola been lethal to humans, Preston is quite right in arguing that it would have posed a terrifying health threat. But not that terrifying, since airborne Ebola would still face the same selection pressures as normal Ebola. There are strains of influenza virus, for example, that are capable of killing just as quickly and as implacably as Ebola. But when flu season comes every year to America, the flu strain that ends up infecting most people is so weakened that it kills only some of the very oldest and frailest of the elderly.

Why? Because a very nasty flu virus simply cannot survive for very long. The people who get infected with it get sick very quickly, and so severely that they go home and lie in their beds. The strain dies with them. And the strains that survive are the milder ones, the ones that keep the infected well enough that they can still go to work and keep on infecting others. The 1918 strain was, in some ways, an abberation. Because of wartime conditions, it started out nastier—and stayed nastier longer—than flu usually does. But even that virus, as vicious a virus as we have ever seen, eventually hit a wall. Airborne Ebola would, like the 1918 flu virus, cut a deadly swath through those at the center of the epidemic. But Ebola, like the flu, mutates rapidly, producing a wide variety of strains in intense evolutionary competition, and so there is every reason to believe that it, too, would soon burn itself out.

What would a real Andromeda Strain look like? It would be highly infectious like the flu, spread through casual contact. But it would also have to be structured in such a way as to avoid the kind of selection bias that usually exists against virulent strains. For that reason, it would need to move stealthily through its host, infecting so silently that the victim would not know to take precautions, and so slowly that the victim would have years in which pass on the infection to someone else.

The Andromeda Strain, in short, the virus that really could kill 80 or 90 percent of humanity, would be an airborne version of HIV. In fact, doomsday types have for years been conjuring up this possibility for the end of mankind. The problem, however, is that it is very difficult to imagine how such a super-virus could ever come about. For a start, it is not clear how HIV could become airborne and still be lethal. (This was the argument of Howard Temin, the late Nobel Prize-winning virologist.) What makes HIV so dangerous is that it seeks out and selectively kills the key blood cells of the human immune system. To be airborne, it would have to shift its preference to the cells of the respiratory system. (Ebola, which is not nearly so selective, probably doesn't need to change personality to become airborne.) How, then, could it still cause AIDS? Why wouldn't it be just another cold virus?

Then there is the problem of mutation. To become airborne, HIV would have to evolve in such a way as to become more durable. Right now the virus is highly sensitive to changes in temperature and light. But it is hardly going to do any damage if it dies the moment it is coughed into the air and exposed to ultraviolet rays. HIV would have to get as tough as a cold virus, which can live for days on a countertop or a doorknob. At the same time HIV would have to get more flexible. Right now HIV mutates in only a limited manner. The virus essentially keeps changing its clothes, but its inner workings stay the same. It kills everyone by infecting the same key blood cells. To become airborne, it would have to undergo a truly fundamental transformation, switching to an entirely different class of cells. How can HIV make two contradictory changes at the same time, becoming both less and more flexible?

This is what is wrong with the Andromeda Strain argument. Every infectious agent that has ever plagued humanity has had to adopt a specific strategy, but every strategy carries a corresponding cost, and this makes human counterattack possible. Malaria is vicious and deadly, but it relies on mosquitoes to spread from one human to the next, which means that draining swamps and putting up mosquito netting can all but halt endemic malaria. Smallpox is extraordinarily durable, remaining infectious in the environment for years, but its very durability, its essential rigidity, is what makes it one of the easiest microbes to create a vaccine against. AIDS is almost invariably lethal because its attacks the body at its point of great vulnerability, that is, the immune system, but the fact that it targets blood cells is what makes it so relatively uninfectious.

I could go on, but the point is obvious. Any microbe capable of wiping us all out would have to be everything at once: as contagious as flu, as durable as the cold, as lethal as Ebola, as stealthy as HIV and so doggedly resistant to mutation that it would stay deadly over the course of a long epidemic. But viruses are not, well, superhuman. They cannot do everything at once. It is one of the ironies of the analysis of alarmists such as Preston that they are all too willing to point out the limitations of human beings, but they neglect to point out the limitations of microscopic life forms.

If there are any conclusions to be drawn about disease, they are actually the opposite of what is imagined in books such as The Hot Zone and The Coming Plague. It is true that the effect of the dramatic demographic and social changes in the world over the past few decades is to create new opportunities for disease. But they are likely to create not homogeneous patterns of disease, as humans experienced in the past, so much as heterogeneous patterns of disease. People are traveling more and living in different combinations. Gene pools that were once distinct are mixing through intermarriage. Adults who once would have died in middle age are now living into their 80s. Children with particular genetic configurations who once died at birth or in infancy are now living longer lives. If you talk to demographers, they will tell you that what they anticipate is increasing clusters of new and odd diseases moving into these new genetic and demographic niches. Rare diseases will be showing up in greater numbers. Entirely unknown diseases will emerge for the first time. But the same diversity that created them within those population subgroups will keep them there. Laurie Garrett's book is mistitled. We are not facing "the coming plague." We are facing "the coming outbreaks."

V.

Illness, as Susan Sontag has shown, is often metaphor. Cancer is saddled with connotations of embarrassment or punishment, and AIDS, as Sontag wrote in "AIDS and Its Metaphors," has come to assume that same position, to be described as a disease caused by an infectious agent, an enemy, from the outside. "This is the language of political paranoia, with its characteristic distrust of a pluralistic world," and it is such language that has made it difficult to combat the discrimination and stigma that surround HIV. It is not difficult to see that Ebola has fallen prey to the same process.

Judging by Preston and company, Ebola is not simply a disease. It is a punishment for our environmental crimes, nature's curse against humanity. And, with this added weight of metaphor, this most marginal of viruses has become the symbol of biological apocalypse. "The most terrifying diseases are those perceived not just as lethal but as dehumanizing, literally so," Sontag writes. The rabies phobia in nineteenth-century France, marked by countless cases of imagined infection, was driven by the fantasy that the disease "unleashed uncontrollable sexual, blasphemous impulses." Cholera was more feared than smallpox in the nineteenth century, despite the fact it killed far fewer people,

because of the suddenness with which it struck and the indignity of the symptoms: fulminant diarrhea and vomiting, whose result anticipated the horror of post-mortem decomposition. Within several hours radical dehydration shrank the patient into a wizened caricature of his or her former self, the skin turned bluish black.

Sontag could just as easily be describing Ebola. The difference, of course, is that AIDS and cancer and cholera are genuine problems. Those who fantasize about them, or construct metaphors about them, do so on the basis of experience. Ebola, and the mythical Andromeda Strain that it is supposed to portend, are imaginary threats.

There are any number of explanations for what has created our epidemic obsession. Hysteria is cyclical, and there is clearly the same kind of social insecurity afoot today as there was in paranoid times past. But let us consider just what the contemporary hysteria exposes about our attitude toward medicine. To read accounts of the earliest successful advances in medical science is to be struck by the frequency with which solutions preceded understanding. Nobody knew exactly why the earliest smallpox vaccine worked, they just knew that it prevented smallpox. There was something very comforting about this. It served to bolster the idea in the public that there was something magical about medicine: Even when what we knew did not add up to a solution, a solution could still be found.

The relationship between medical solutions and medical understanding has now been reversed. To attend any of the massive international AIDS conferences in the early 1990s was to be struck by just how incredibly detailed our knowledge of HIV and AIDS has become. Rarely a month goes by without one of the major medical journals announcing the discovery of a new gene implicated in cancer or the decoding of some pathological cellular process. For all these announcements and alleged breakthroughs, however, medical science's actual progress in prolonging or saving the lives of those with cancer or AIDS has appeared stubbornly slow. The dominant symbols of technological advancement over the past two decades have been diagnostic tools: CAT scans, PET-scans, MRIs, advanced mammography, ultrasound. Physicians seem to have improved their ability to diagnose disease much faster than their ability to treat it.

It goes without saying that this impression about contemporary medicine is inaccurate. The reason that medicine seems to be accumulating knowledge faster than it is accumulating mastery is that we pay a lot more attention to the accumulation of knowledge than we ever did. No one wrote about Koch's preliminary experiments with smallpox in the nineteenth century in the newspapers of the day. Cancer is also a harder problem than smallpox ever was. But these subtleties are easily overlooked. The truth is that Americans have come to fundamentally change their view of medicine. It is not that they have lost faith in it. They have redefined it. Medicine is no longer the savior, it is the explainer. Scientists do not cure, they investigate. The idea that medicine works magic is disappearing. Even when what we know appears to add up to a solution, there is no longer any confidence that a solution can be found.

This is what the Ebola paranoia is all about. The heroes of The Hot Zone are not people working to treat or to cure the virus. They are the people who track its progress around the globe, who set out on expeditions through the forest to find its natural host. They are analysts, describers. On the question of what to do about Ebola, how to prevent another outbreak, how to better treat the disease, they are largely silent. This is a striking omission in a work of science journalism. Before Preston, the popular science book was almost always a mystery story: A vexing scientific puzzle arises, a hero shuns family and sleep to investigate, a solution is found. But The Hot Zone is not a mystery story. It is a horror story, and at the end of the story the horror remains at large.

The Coming Plague, too, is almost entirely given over to description. For 600 pages, Garrett brings science in all its glory to bear on the question of why the variety of scourges facing mankind arose just when they did. But when it comes to writing about solutions, she delivers twenty-five pages. And her final advice is so broad as to be useless: Man must be nicer to nature. Books more scrupulous than Preston's and Garrett's would have pointed out that what we have learned about infectious disease suggests that we should not fear extinction, that our ability to understand a threat and act accordingly is what separates us from the chickens of Pennsylvania. But what we have been given, instead, and what we have accepted uncritically, is medicine in retreat, and science as the passive observer of events. In this incarnation, science excels only at making the unimaginable imaginable and the incomprehensible comprehensible. It does not inspire courage. It inspires fear. It is good at creating helplessness. It is not good at dispelling it.