Since the first avian influenza outbreaks hit the U.S. early this year, health and agriculture experts have struggled to track the virus’s spotty path as it spreads in dairy cow herds and an unknown number of humans. Infection risk still seems low for most people, but dairy workers and others directly exposed to cows have been getting sick. Canada’s first human case was just reported, in a teenager who is in critical condition. To get a better handle on the unsettling situation, scientists are picking up a pathogen-hunting tool that’s…
