When Alexander the Great stood at the gates of Babylon in 323 B.C., the story goes, a flight of ravens fell dead at his feet.

It was a bad omen, according to the soothsayers. Within two weeks, the conqueror of an empire that stretched from Greece to India was dead at age 32 of a mysterious illness.

Doctors and historians have speculated for centuries about the cause of this battle-hardened warrior’s death. In 1998, two University of Maryland Medical Center physicians said he probably died of typhoid, which can cause the chills, fever, abdominal pain and delirium that Alexander suffered.

But today, across the Potomac, the Virginia Health Department’s chief epidemiologist says those dying ravens weren’t omens, but clues. Alexander may have been history’s most famous victim of West Nile virus, John Marr says.

The typhoid diagnosis was "brilliant," Marr said, "but I have the advantage of hindsight. In 1998, they didn’t realize that looking for dead crows was a good early warning system for West Nile."

Marr and a colleague, Colorado epidemiologist Charles Callisher, outlined the West Nile theory in the December issue of the journal Emerging Infectious Diseases. Their analysis drew lavish praise from one author of the typhoid hypothesis.

"I thought it was wonderful. I loved it," said the University of Maryland’s David Oldach. However, he doesn’t buy it.

"I don’t really believe he died of West Nile virus," Oldach said. "On the other hand, the beauty of these historical investigations is that no one can ever prove you wrong."

By the time Alexander conquered Babylon, near the site of modern Baghdad, he’d had a tough year — including a spear in the chest.

"He also had been knocked on the head," Marr noted. "His significant other had died of a fever. He was severely depressed. I think he was chugging about a half-gallon of wine."

Two centuries later, the Greek biographer Plutarch wrote that Alexander’s counselors told him to enter Babylon from the east. That required him to pass through a swamp where mosquitoes breed. The insects carry West Nile virus, passing it along to birds — especially crows — which help spread the disease.

Mosquitoes were common, Marr said. Ancient writers described many cases of malaria, another mosquito-borne illness. The epidemiologist also concluded that ancient Babylon was hot enough for mosquitoes to spread the virus in late May instead of in late summer, when the disease usually occurs there.

As Alexander reached the walls of Babylon, Plutarch wrote, "he saw a large number of ravens flying about and pecking one another, and some of them fell dead in front of him."

Other analysts ignored or dismissed that detail, assuming Plutarch made it up. Ether that, Marr said, or the crows had the deadly virus.

At a banquet in Babylon, the conqueror drank 11 pints of wine and grabbed his chest, stricken. In the ensuing days, he suffered chills, constant fever and horrible abdominal pain. Many diseases exhibit those symptoms, but there was one unique factor: a strange paralysis that began in Alexander’s feet and slowly moved up his body.

That clinched the diagnosis for Marr, whose curiosity had been piqued by Oldach’s original article in the prestigious New England Journal of Medicine.

To check the diagnosis, Marr and his colleague entered Alexander’s symptoms and the clue about the ravens into an online diagnostic program and got an answer: West Nile.