"You are not going to believe this one," he told Ron Fouchier, a virologist at the Erasmus Medical Center in Rotterdam. "I think we have an airborne H5N1 virus."
The news, delivered one afternoon last July, was chilling. It meant that Dr. Fouchier's research group had taken one of the most dangerous flu viruses ever known and made it even more dangerous - by tweaking it genetically to make it more contagious.