But health officials have warned that with continued exposure to people, the virus could mutate further and develop the ability to pass directly from humans to humans.

• 但是同时，世界卫生组织官员也警告，随着禽流感病毒持续与人类接触，那种病毒会更进一步变异，不断得成长为一种可以直接在人群中传播的病毒。