The Hospital for Tropical Diseases in Ho Chi Minh City, where Dr. Jeremy Farrar works, has treated about two dozen people with avian influenza in the last three years.

Dr. Jeremy Farrar. The Hospital for Tropical Diseases in Ho Chi Minh City, where Dr. Farrar works, has treated about two dozen patients with avian flu.

With that tiny number, Dr. Farrar and his Vietnamese colleagues probably have more clinical experience than any other doctors with the A(H5N1) virus — the dreaded germ that international health officials fear may ignite the next flu pandemic.