Leaning over a metal cage stuffed with live hens in Shanghai, Ran looked for just the right specimen for her chicken soup. The 60-year-old was shopping at one of China's wet markets, where sales of freshly slaughtered, unpackaged meat have become the focus of an investigation into an outbreak of a potentially deadly lung virus.

Four people have died and more than 200 have been infected, including fifteen medical professionals. The new virus is a cousin of the cause of severe acute respiratory syndrome, or SARS, which killed almost 800 people 17 years ago.

Known as 2019-nCov, the new coronavirus was first found in people who shopped or worked at a wet market in the central city of Wuhan. The pathogen may have been transmitted to humans from live animals sold there.