As many as ninety per cent of those infected with Ebola will die. There is no cure or treatment. There are several vaccines under development; in early animal tests, more than one has shown promise. But it will be years before they are ready for humans. Until then, if you get Ebola, you are most likely done for. The virus can eat away at capillaries and blood vessels, causing you to drown in your own blood. As David Quammen wrote in “Spillover,” the definitive book about the origin and evolution of human epidemics, “Advisory: If your husband catches an Ebola virus, give him food and water and love and maybe prayers but keep your distance, wait patiently, hope for the best—and, if he dies, don’t clean out his bowels by hand. Better to step back, blow a kiss, and burn the hut.”

Still, Ebola’s more prosaic symptoms—abdominal and muscle pain, fever, headache, sore throat, nausea, and vomiting—also apply to at least a dozen other conditions. Could an infected airline passenger make it to the United States? Absolutely. But in this country every doctor and nurse in every clinic and hospital uses gowns, latex gloves, masks, and disinfectants. Those precautions are rarely available in the parts of Africa where the epidemic has been most severe. Ebola is contagious only when it is symptomatic, and by that time people are almost invariably too sick to travel. (Patrick Sawyer, the only American to die so far in this outbreak, collapsed after a flight from Liberia to Lagos. He was planning to fly next to Minnesota. He never got on that plane.)

“I wouldn’t be worried to sit next to someone with the Ebola virus on the Tube, as long as they don’t vomit on you or something,” Peter Piot told Agence France-Presse this week. Piot, the director of the London School of Hygiene and Tropical Medicine, was one of the two people who, in 1976, discovered Ebola. He then ran the United Nations’ AIDS program for more than a decade. “This is an infection that requires very close contact,” he said.