The experiment of whether H5 can ever be successful in human populations is happening before our eyes,” Seema Lakdawala, a flu virologist at Emory University, told me. “And we are doing nothing to stop it.

Medical experts advise that people should get a vaccine for the bird flu when it becomes commercially available. One doctor said the most at-risk patients should be first.

The bird flu virus circulating among cows, poultry and wild birds isn't yet a threat to the general public, but experts say if and when that will change is impossible to predict — and that if things do get bad,