Background

At the end of December, public health officials from China informed the World Health Organization that they had a problem: an unknown new virus was causing pneumonia-like illness in the city of Wuhan. They quickly determined that it was a coronavirus and that it was rapidly spreading inside and outside Wuhan. Scientists think this new virus first became capable of jumping to humans at the beginning of December. It originally seemed the virus first infected people at a seafood market in Wuhan and spread from there. But an analysis of early cases of the illness, published on 24 January 2020, found that the first patient to get sick did not have any contact with the market. Experts are still trying to trace the source of the outbreak.