Although the Ebola virus might remain mostly confined to West Africa, it has infected the Western imagination. This eruption of uncontrolled nature into what developed nations consider serene modernity is more disturbing to the emotional serenity of multitudes than it is threatening to their physical health.

Perhaps the world periodically needs an equivalent of the 1755 Lisbon earthquake, a chastening reminder that nature still has something to say about what human beings proudly, and prematurely, call “the conquest of nature.” The earthquake disturbed Europe’s Enlightenment serenity: Perhaps God has not really ordained a benevolently ordered universe. This should not have been news to Europe, which in the 14th century had lost more than half of its population to the Black Death plague, and had subsequently endured many lesser but nevertheless devastating epidemics.

In America, the first modern nation and the nation most committed to the modern project of taming nature’s capriciousness, the AIDS epidemic of the early 1980s was particularly traumatic. This was so even though the public health threat from the disease was limited because the primary means by which it was transmitted were known risky behaviors involving sex or needles shared by drug users.

AIDS disabused Americans of their polio paradigm. The 1950s success of the Salk vaccine in removing the terror of polio had encouraged the belief that pharmacology could slay all infectious diseases.

The Black Death probably spread through Europe by land and on fleas carried by rats brought by ships to Mediterranean ports, and transportation also contributed to the spread of AIDS. HIV, the virus that causes AIDS, probably came from chimpanzees in Africa and infected humans who hunted them around the 1930s. HIV was spread by truckers who patronized prostitutes along Africa’s improved roads. Boeing and Airbus, two manufacturers of the aircraft that made intercontinental travel accessible to multitudes, have thereby complicated public health officials’ task of quarantining diseases. The man tentatively identified years ago as “Patient Zero,” who supposedly introduced HIV to America, was an Air Canada flight attendant.

Nowadays, so many terrible deeds are reflexively called terrorism that the term is becoming a classification that no longer classifies. Remember, terrorists are in the terror business, the essence of which is random horror.

A nuclear weapon in a terrorist’s hands would be a nightmare, but not necessarily the worst such. The scientific infrastructure for the manufacture of such a weapon is expensive and complex, and the means of delivering it to a target can be, too. A biological weapon can be delivered by a terrorist carrying a vial of smallpox in his pocket.

Epidemics – silent and invisible during their incubation, swift and unpredictable in their trajectories – are devastating terror weapons, as participants discovered from Dark Winter. This 13-day simulation of a bioterrorism attack – it postulated the release of smallpox in Oklahoma City, Philadelphia and Atlanta – was conducted in June 2001.

Smallpox is easily transmitted by breathing air exhaled by infected persons, and the fatality rate is about 30 percent. Furthermore, there is an incubation period of seven to 17 days, during which infected persons show no symptoms. Dark Winter concluded that a smallpox virus released in those three cities would reach 25 states and at least 10 other countries within two weeks, bringing unprecedented panic with it.

In 1947, a single American smallpox case caused 6.4 million Americans, including President Harry Truman, to be vaccinated. According to a University of Pittsburgh Medical Center report, “There has never been a smallpox outbreak in such a densely populated, highly mobile, unvaccinated population” as today’s America. The UPMC report says smallpox vaccinations in America stopped in 1972, and vaccine production facilities were closed in the 1980s. Since 9/11, production has resumed.

A single smallpox case in Yugoslavia in 1972 prompted the vaccination of almost all 20 million Yugoslavs. In 1980, the World Health Organization declared smallpox, a killer of hundreds of millions, eradicated. Today, supposedly only America and Russia retain samples of the smallpox virus. Last month, six glass vials of it were found in a storage room at the National Institutes of Health in suburban Washington.

Amid this month’s commemorations of the 100th anniversary of the beginning of history’s most calamitous man-made event, World War I, remember its ending: A worldwide influenza pandemic arose from wartime conditions. It began in 1918 and killed more people in a year (about 50 million) than the war killed (about 16 million, military and civilian) in four years. Nature, Ebola reminds us, remains a creative danger.

© 2014, Washington Post Writers Group