On a sunny September morning in 2011, at a conference on the Mediterranean island of Malta, virologist Ron Fouchier made an announcement that shook the scientific world. His lab, he said, had taken H5N1 avian influenza virus — which kills around 60 percent of people with known cases, but which cannot spread easily from person to person — and altered it to transmit among mammals.
He had created, he told a reporter later that year, "probably one of the most dangerous viruses you can make."
