It started on a small military base in central Kansas, when one soldier came down with a fever. Within a few hours, about 100 soldiers had reported to the Fort Riley infirmary with the same complaint.
By 1919, one year later, the so-called Spanish flu had spread around the world, killing an estimated 50 million people, with more than 500,000 dead in the U.S. (That included 195,000 just in the single month of October 1918.) The disease took more lives than the black plague, and more than all the wars of the 20th century combined.
In especially virulent cases, many of the afflicted died just hours after feeling their first symptoms. Death estimates vary because people often died and were buried before they could be named or counted.
Health experts are concerned that the Spanish flu that ravaged the world has many similarities to the avian flu now found throughout Southeast Asia.
The 1918 flu strain itself originated as an avian flu that mutated into a form that could jump between humans. And the 1918 strain, according to research published this week in the scientific journals Nature and Science, has several of the same genetic mutations as the current avian flu strain.
Could a deadly pandemic happen again? Some doctors say yes.
Dr. William Schaffner, chairman of preventive medicine at Vanderbilt University Medical Center in Nashville, Tenn., says there are some parallels between the avian flu and the Spanish flu.
"It was a new influenza strain at the time," Schaffner said of the Spanish flu. "The population of people on the whole planet had no experience with it."
The longer a flu strain has been around, the more time people have had to build up resistance to it.
Another striking parallel between the two diseases is the victims. While most flu viruses strike the very young and very old, the Spanish flu affected many between the ages of 20 and 35. The avian flu has followed a similar pattern.
"It particularly had a high fatality rate among young, healthy people," Schaffner said of the 1918 pandemic.
The flu that struck Fort Riley killed 48 soldiers in the spring of 1918. It might have been contained there but for one thing: World War I.
Soldiers gathering in military bases were shipped out to Europe that year, bringing with them the deadly virus. Though the Spanish flu was spread aboard ships and in the trenches and military camps of Europe and America, Schaffner notes the avian flu might be dispersed even more quickly and easily today.
"It would spread much more rapidly on airplanes," Schaffner notes. "The potential for rapid spread is much greater today."
With the Spanish flu spreading uncontrolled in cities and rural areas alike, a breakdown in the social fabric of many communities came quickly.
Orphans wandered the streets while bodies piled up in makeshift morgues. Coffins were in short supply so open carts picked up the dead from front porches. Many bodies were hurriedly buried in mass graves dug by steam shovels.
Panicked communities across the country enacted a variety of laws to address the invisible enemy. Public gatherings of all kinds – even in saloons – were outlawed. Handshakes became illegal. Funerals were not allowed to last more than 15 minutes. Face masks of thin gauze (though worthless against the virus) were required by law in some areas.
"In San Francisco, you couldn't go out in the street without a mask," said Alfred W. Crosby, historian and author of "America's Forgotten Pandemic: The Influenza of 1918."
"The important thing is the measures that were taken were ineffective and taken too late," Crosby said.
Still, some tried to continue with life as if the pandemic didn't exist. In Philadelphia, a mass rally was organized to sell war bonds, despite the concerns of some city officials.
The rally, attracting a crowd estimated at 200,000, proved a fertile ground for the virus. In that hard-hit city, some 12,000 deaths from "the Spanish Lady" were reported.
Medical facilities were strained beyond the breaking point as many doctors and nurses were serving overseas. Schools, businesses, farms and factories were shuttered as workers and customers were afraid to leave the house – or were dead.
The military fighting in Europe was also decimated by the virus. In many units, the flu killed more men than the enemy.
In the absence of any cure or treatment, paranoia, nationalism and suspicion ran rampant. "In 1918, people tried to blame it on the German U-boats who came up to the coast and gave everyone the flu," said Crosby.
The Spaniards called it the French flu. The name Spanish flu likely came from the fact that Spanish newspapers – uncensored by authorities because Spain did not participate in WWI – were among the first to report large numbers of deaths from the disease.
Without a cure, the desperate reached for a number of remedies. Some hung balls of camphor around their necks. Others ate lumps of sugar flavored with kerosene.
"People did everything you could think of," said Crosby. His favorite cure of the time: "Tie a red ribbon around your right arm."
Though smaller waves of the Spanish flu came and went after 1918, the disease left almost as quickly as it arrived – anyone exposed to the illness had either developed a resistance or died.
Health officials worldwide have expressed alarm at the vigor of the avian flu, and doctors debate whether society is better equipped to deal with a pandemic than in 1918.
"We're in a much better position now than we were then," said Dr. Stephen Baum, Chairman of the Department of Medicine and infectious disease specialist at Beth Israel Medical Center in New York City.
"There are some antiviral agents that can probably have a beneficial effect on ameliorating the disease [avian flu] a bit and decreasing transmission," Baum said. Both oseltamivir (Tamiflu) and zanamivir (Relenza) have been shown to be effective against influenza.
"These things can be identified in remarkably short time these days," Baum added, noting that the SARS virus was identified in less than six weeks, whereas it took nine to 12 months for the cause of Legionnaire's disease to be identified after it appeared in 1976.
Baum also notes that the role of hand washing and personal hygiene is better understood today than in 1918.
"We've obviously come a long way," Baum said. "It doesn't have to happen again."
But doctors also admit that much work remains to prevent another deadly pandemic.
Vanderbilt's Schaffner concedes that antiviral medication can be effective, "if we have enough and we can get it to people in time." Stockpiles of antiviral medication in the U.S. are perilously low, according to some analysts, and the treatment is only effective if started within 48 hours of infection.
"You've got to really invest vast resources right now to protect us from a pandemic," said Schaffner.
Baum acknowledges that a vaccine to prevent the avian flu remains elusive.
"There's nobody making vaccines anymore because the profitability is low and the liability is high," said Baum. "There's got to be government support for vaccine development and production."
Many countries are slow to admit that an infectious health problem is brewing within their borders. "On a political level, we need the places that have a problem with this [infectious diseases] to be upfront about it," said Baum. "Certainly with AIDS, many countries have been reluctant in admitting they have AIDS."
And what if a pandemic were to strike again?
Crosby and Schaffner compare the nation's response to Hurricanes Katrina and Rita to our response to a possible flu pandemic.
"When I look at the Gulf Coast after the hurricane, I'm not encouraged," Crosby said. "Today we have news 24/7 and people would just go into hysteria."
"It would be a hurricane to hit the entire country," said Schaffner. "It would be a punch to the solar plexus and it would take us a long time to recover."
"The whole world economy would shudder," Schaffner added.