In Haskell County, Kansas, the winter of 1917-1918 was hard. Many people came down with a flu that was unusually serious. We don't know exactly how many of Haskell County flu victims died that winter, but it was enough to alarm the local doctor. He was so concerned about the number of local and deadly cases of flu that he wrote an alert to the government.

Of course, that didn't stop the government from drafting young men from

The 1918 flu was the most lethal disease pandemic in history -- killing 20 to 100 million people worldwide, most of them in the Fall of 1918.

It's now being examined and debated with new urgency, thanks to the threat of a bird flu pandemic.

According to evolutionary biologist Paul Ewald, author of Evolution of Infectious Disease and Plague Time: How Stealth Infections Cause Cancers, Heart Disease and Other Deadly Ailments (both great books well worth reading), the 1918 flu was so much more lethal than ordinary flu because it appeared and evolved at the Western Front of World War I Europe's brutal trench war.

The more advantageous it is for infections to keep us alive and feeling well enough to walk around, the safer they are. The common cold is irritating but we can still go to work with it -- the better to sneeze and spread cold germs to our co-workers.

The more advantageous it is for infections to disable and kill us, the more they will do so. Malaria makes us so sick because it spreads by mosquitoes -- who find it easier to bite people who're too sick to slap mosquitoes. Who then go spread the infection to a healthy person.

During the 1918 flu, soldiers in Europe lay sick in crowded trenches where they easily spread the flu to other soldiers even though they were too sick to walk and many soon died. When transported to medical care, they were crowded into trucks and train cars with other sick and wounded soldiers. And arrived at military hospitals crowded with more sick and wounded soldiers.

Therefore, the 1918 flu virus had every evolutionary incentive to evolve into a strain highly lethal to people.

But is that the whole story? According to Ewald, we are not in danger of a bird flu pandemic -- or at least, not one as deadly as 1918 -- because there is no similar war going on today.

So should we all forget about bird flu and start worrying about Iran and global warning?

Ewald uses sources from the 1940s that give France as the origin of the 1918 flu.

In The Great Influenza: The Epic Story of the Deadliest Plague In History John M. Barry discusses the work of Dr. Edwin Johnson, editor of THE JOURNAL OF INFECTIOUS DISEASE, who studied the 1918 soon after it happened and published EPIDEMIC INFLUENZA in 1927.

Dr. Johnson also discards the theory (that some have given) that the 1918 flu originated in China and spread to Europe via imported laborers. Yet he also could not find evidence that it started in Europe.

In Haskell County, Kansas, the winter of 1917-1918 was hard. Many people came down with a flu that was unusually serious. We don't know exactly how many of Haskell County flu victims died that winter, but it was enough to alarm the local doctor. He was so concerned about the number of local and deadly cases of flu that he wrote an alert to the government.

Of course, that didn't stop the government from drafting young men from H

The more advantageous it is for infections to keep us alive and feeling well enough to walk around, the safer they are. The common cold is irritating but we can still go to work with it -- the better to sneeze and spread cold germs to our co-workers.

The more advantageous it is for infections to disable and kill us, the more they will do so. Malaria makes us so sick because it spreads by mosquitoes -- who find it easier to bite people who're too sick to slap mosquitoes. Who then go spread the infection to a healthy person.

During the 1918 flu, soldiers in Europe lay sick in crowded trenches where they easily spread the flu to other soldiers even though they were too sick to walk and many soon died. When transported to medical care, they were crowded into trucks and train cars with other sick and wounded soldiers. And arrived at military hospitals crowded with more sick and wounded soldiers.

Therefore, the 1918 flu virus had every evolutionary incentive to evolve into a strain highly lethal to people.

But is that the whole story? According to Ewald, we are not in danger of a bird flu pandemic -- or at least, not one as deadly as 1918 -- because there is no similar war going on today.

So should we all forget about bird flu and start worrying about Iran and global warning?

Ewald uses sources from the 1940s that give France as the origin of the 1918 flu.

In The Great Influenza: The Epic Story of the Deadliest Plague In History John M. Barry discusses the work of Dr. Edwin Johnson, editor of THE JOURNAL OF INFECTIOUS DISEASE, who studied the 1918 soon after it happened and published EPIDEMIC INFLUENZA in 1927.

Dr. Johnson also discards the theory (that some have given) that the 1918 flu originated in China and spread to Europe via imported laborers. Yet he also could not find evidence that it started in Europe.

In Haskell County, Kansas, the winter of 1917-1918 was hard. Many people came down with a flu that was unusually serious. We don't know exactly how many of Haskell County flu victims died that winter, but it was enough to alarm the local doctor. He was so concerned about the number of local and deadly cases of flu that he wrote an alert to the government.

Of course, that didn't stop the government from drafting young men from

During the 1918 flu, soldiers in Europe lay sick in crowded trenches where they easily spread the flu to other soldiers even though they were too sick to walk and many soon died. When transported to medical care, they were crowded into trucks and train cars with other sick and wounded soldiers. And arrived at military hospitals crowded with more sick and wounded soldiers.

Therefore, the 1918 flu virus had every evolutionary incentive to evolve into a strain highly lethal to people.

But is that the whole story? According to Ewald, we are not in danger of a bird flu pandemic -- or at least, not one as deadly as 1918 -- because there is no similar war going on today.

So should we all forget about bird flu and start worrying about Iran and global warning?

Ewald uses sources from the 1940s that give France as the origin of the 1918 flu.

In The Great Influenza: The Epic Story of the Deadliest Plague In History John M. Barry discusses the work of Dr. Edwin Johnson, editor of THE JOURNAL OF INFECTIOUS DISEASE, who studied the 1918 soon after it happened and published EPIDEMIC INFLUENZA in 1927.

Dr. Johnson also discards the theory (that some have given) that the 1918 flu originated in China and spread to Europe via imported laborers. Yet he also could not find evidence that it started in Europe.

In Haskell County, Kansas, the winter of 1917-1918 was hard. Many people came down with a flu that was unusually serious. We don't know exactly how many of Haskell County flu victims died that winter, but it was enough to alarm the local doctor. He was so concerned about the number of local and deadly cases of flu that he wrote an alert to the government.

Of course, that didn't stop the government from drafting young men from

So should we all forget about bird flu and start worrying about Iran and global warning?

Ewald uses sources from the 1940s that give France as the origin of the 1918 flu.

In The Great Influenza: The Epic Story of the Deadliest Plague In History John M. Barry discusses the work of Dr. Edwin Johnson, editor of THE JOURNAL OF INFECTIOUS DISEASE, who studied the 1918 soon after it happened and published EPIDEMIC INFLUENZA in 1927.

Dr. Johnson also discards the theory (that some have given) that the 1918 flu originated in China and spread to Europe via imported laborers. Yet he also could not find evidence that it started in Europe.

In Haskell County, Kansas, the winter of 1917-1918 was hard. Many people came down with a flu that was unusually serious. We don't know exactly how many of Haskell County flu victims died that winter, but it was enough to alarm the local doctor. He was so concerned about the number of local and deadly cases of flu that he wrote an alert to the government.

Of course, that didn't stop the government from drafting young men from

In Haskell County, Kansas, the winter of 1917-1918 was hard. Many people came down with a flu that was unusually serious. We don't know exactly how many of Haskell County flu victims died that winter, but it was enough to alarm the local doctor. He was so concerned about the number of local and deadly cases of flu that he wrote an alert to the government.

Of course, that didn't stop the government from drafting young men from Haskell County -- who were sent to Camp Funston for training before shipping them off to France.

So it's quite possible that the 1918 flu first infected people in Haskell County, Kansas.

It appears that it did evolve once it was in Europe. The first wave of it hit the soldiers in the spring. It was known as the 3 day flu because large numbers of them caught it, were sick for 3 days and then recovered.

Then it went unnoticed until around September 1918 -- when it spread throughout the world and in 3 months killed many more people than the war itself. From at peace Spain (which was unfairly blamed for it) to the South Pacific to remote Eskimo villages in Alaska.

Perhaps the deadly 1918 flu had its deadly origins for BOTH reasons:

1. It was a mutated avian flu that people did not have any acquired immunity for.

2. Wartime conditions encouraged it to retain and/or increase its lethality, by rewarding it for disabling and killing soldiers so fast and easily.

What does this mean for bird flu today?

We already know it's a mutated avian flu we have no acquired immunity for. It kills over half of its human victims.

There is no major, intense war underway -- but many people in large megacities of the developing world from Rio to Calcutta live in extreme population density. One sick person lying in the corner of a corrugated iron hovel could infect many close family members and neighbors. If a pandemic struck, many would be transported to large and overcrowded medical centers.

In such conditions, a bird flu mutation would likely retain or evolve its extreme lethality.

And what if it was "only" as lethal as the virus that caused the 1968 "Hong Kong" virus?

According to the CDC, the 1968 virus would today kill 2 to 7 million people around the world. From 89,000 to 207,000 people just in the U.S. That would not be a worst case scenario but it would certainly cause a lot of fear and concern.

Therefore, bird flu does not have to evolve into a strain as deadly as 1918, to pose a threat to millions of people around the world. Even without a major world war, we are at risk from a bird flu pandemic.