A skull discovered at a sacred Aztec temple. A new study analyzed DNA extracted from the teeth of people who died in a 16th century epidemic that destroyed the Aztec empire, and found a type of salmonella may have caused the epidemic.
Health workers killed chickens in a Hong Kong market in 2014 in an effort to stop the spread of H7N9 flu. It's being watched closely as a virus that might spark a pandemic outbreak.
A patient with the H7N9 avian flu is treated in a hospital in Wuhan, in central China's Hubei province, in February of this year. The 2017 outbreak was the deadliest in China since H7N9 first appeared in humans in 2013.