Avian flu strain shows transmissibility among mammals

A highly contagious avian flu is infecting birds all over the globe. In the U.S., farmers have lost, or had to kill, over 58 million birds to try and prevent the spread of the virus. The H5N1 strain hasn’t caused any serious threat to humans, but outbreaks in some mammals raised concerns about the potential to spread further. Influenza researcher Scott Hensley joined William Brangham to discuss.