It was September 2004. An 11-year-old girl had fallen ill after playing with some sick chickens. At first, it seemed like a bad case of the flu. But the girl kept getting sicker.

In the hospital, her mother held her for hours. Then early in the morning, the girl died. Soon, her mother began to feel sick. The mother died, too.

Dr. Dowell is an epidemiologist. His job is to figure out what makes people sick—and to keep diseases from spreading to others. He feared that the little girl and her mother had died from a rare bird flu.

If Dowell was right, it could mean big trouble.