When researchers created a vaccine, they largely put an end to the 2013 bird flu pandemics in chickens, capping a worldwide health scare. But now, scientists have found new versions of the viruses in ducks. Researchers recommend vaccinating the nearly 3 billion ducks produced in China each year straightaway.

Virulent Virus

Back in 2013, authorities detected H7N9, a version of the flu that infects birds, in Chinese poultry markets. Soon after, they found the viruses in chicken farms. Th