H5N1 avian influenza, more commonly known as bird flu, has infected more than 100 million birds in the U.S. and almost 500 dairy cattle herds across 15 states. The virus has popped up in mammals including elephant seals,

Wastewater in several Californian cities, including San Francisco and Los Angeles, recently tested positive for bird flu. But understanding disease risk and exposure to humans isn’t so straightforward

A teenager in British Columbia was hospitalized in critical condition with the disease, and officials were working to find out how the person was exposed to the virus.

Canada detected its first human case of the new strain. Sen. Elizabeth Warren (D-Mass.) said Monday that President elect-Trump “and his transition team are already breaking” a law on presidential transition.