In a long-awaited study that helped prompt a
contentious debate over the wisdom of conducting research that has the potential
to help as well as harm, scientists reported Wednesday that they had engineered
a mutant strain of bird flu
that can spread easily between ferrets — a laboratory animal that responds to flu viruses
much as people do.

That means that bird flu has "the potential to
acquire the ability to transmit in mammals," said University
of Wisconsin virologist Yoshihiro Kawaoka, who led the study.