As Dr. Sreyleak Luch drove to work on the morning of Feb. 8, through busy sunbaked streets in Cambodia¡¯s Mekong river delta, she played the overnight voice messages from her team. The condition of a 9-year-old boy she had been caring for had deteriorated sharply, and he had been intubated, one doctor reported. What, she wondered, could make the child so sick, so fast?

¡°And then I just thought: H5N1,¡± she recalled. ¡°It could be bird flu.¡±

When she arrived at the airy yellow children¡¯s ward at the provincial hospital in Kratie, she immediately asked the child¡¯s father if the family had had contact with any sick or dead poultry. He admitted that their rooster had been found dead a few days before and that the family had eaten it.