Webster predicted it would take at least 10 more mutations before the H5N1 virus could potentially begin spreading from human to human, but said there's no way to know when or if that will ever happen.
Webster said much more research is needed to understand the virus' behavior and how it is spread. Research is being hindered, he said, by cultural issues preventing autopsies of victims. In many Asian countries, where most of the human deaths have occurred, many people do not believe in disturbing the body after death.
He said autopsies have been done on only six of the 113 people killed by bird flu since the virus began ravaging Asian poultry stocks in late 2003.