The legacy: It was an annual plague. Every summer, as warm weather set in, New Orleans braced for an outbreak of yellow fever. Those who could afford it got the heck out, fleeing to the Northshore or farther. Those who couldn't, stayed. And they prayed. Nearly every year, hundreds of them would be killed anyway by the so-called "saffron scourge" -- sometimes thousands. Then, in 1900, a team led by Army doctor Walter Reed confirmed a key discovery: It was the mosquitoes. The winged pests weren't just annoying. They were deadly, spreading the virus that caused the disease. That breakthrough...