The next wave of bird flu could be worse than ever

Test finds mutated strain of H7N9 can pass between lab animals through the air

market in Dongguan, China

POULTRY PROBLEMS  So far, most cases of human H7N9 infection have come from exposure to birds, often in live poultry markets. Here, epidemiologists collect samples at a market in Dongguan, China, in 2014.

CDC/Shuqing Zhao, China

A new version of the H7N9 avian influenza virus might be able to cause widespread infection and should be closely monitored, scientists say, although it currently doesn’t spread easily between people.