Was the Swine Flu Epidemic Inevitable?

A Fire That Scorches Us All

Eighty years ago, a sudden mutation in the virus that causes influenza initiated a worldwide epidemic — or pandemic — that in a mere 18 months killed an estimated 25 million to 40 million people around the world. Experts consider the scourge of 1918, known as the Spanish flu, to be the worst natural disaster in history. Entire villages in remote regions like Alaska and the Philippine hinterlands were decimated much the way that Native Americans were wiped out by smallpox in the 1600s. In the U.S., health officials vainly commanded citizens to wear disinfectant-soaked cotton masks in public. Nurses making house calls often encountered scenes, reminiscent of the Black Plague, in which whole families were dead or dying. In Philadelphia, the flu hit so hard that morticians couldn't keep up with the corpses.

One of the most serious outbreaks occurred among the 45,000 recruits stationed at Camp Devens, near Boston, in September 1918. In one month, doctors identified 17,000 cases of influenza and saw nearly 800 fatalities. At another camp, a commander blew his brains out after more than 500 young soldiers died. Some historians speculate that it was Spanish influenza, not politics, that brought the armies of every nation to their knees and ended World War I. The flu of 1918 was biological warfare without rhetoric or national loyalties.

Two-thirds of those who died were young, between the ages of 20 and 40: soldiers packed into crowded troopships on their way to the war in Europe, for instance, and their betrothed, who remained behind. This wave of death shocked the medical establishment, which held that only the elderly, newborns and those already ill — "immunocompromised" in today's medical parlance — were vulnerable to death by flu. Today it seems that the hard lessons of 1918 have been forgotten. The flu is once again considered a nuisance ailment, dangerous to only a few. Recently, however, a group of scientists who study infectious diseases has sounded a warning: Our currently held beliefs about this ancient disease are not only wrong — they're dead wrong.

Hundreds of years ago, Europeans believed that flu outbreaks were determined, or "influenced," by the alignment of the stars. Today we know that influenza is caused by a class of viruses that are among the most infectious pathogens known to man. Particles of influenza viruses literally float in the air for hours after a flu victim has coughed, waiting to be inhaled by other hosts, which can include not just people but also dogs, horses, ferrets, pigs, birds and even some marine mammals. The first flu virus in a human was isolated in 1933, when a laboratory-housed ferret sneezed in the face of a scientist, who then developed the symptoms of influenza.

Once inhaled, the virus infects the cells lining the respiratory tract. In susceptible hosts, the infection will cause a high fever, a painful cough that can turn into pneumonia, body aches and lung pain. A mild case of flu is often difficult to distinguish from a cold, a factor that complicates public-health officials' efforts to determine whether a flu bug has achieved epidemic proportions. Even people who are symptom-less are capable of transmitting it. Not everyone will suffer to the same degree, but everyone is likely to be infected by a new strain, especially viral strains that have undergone significant mutations.

Pathology expert W.I.B. Beveridge, who wrote a natural history of the influenza virus in the 1970s, warned, "There is no known reason why there should not be another catastrophic [pandemic] like that of 1918 or even worse." The flu, he warned, always has the capability of becoming "a global plague: A spark in a remote corner of the world could start a fire that scorches us all." Should a superflu akin to that of 1918 make a comeback now that the population has quadrupled and more than a million people cross international boundaries on jets each day, experts say it could kill hundreds of millions.