Only three and a half weeks ago, China announced the outbreak of a mysterious new coronavirus in the city of Wuhan involving a group of people who’d been exposed to animals at a local food market.

Flash-forward to Friday: The number of cases of 2019-nCoV, as the virus is known, has leaped to more than 800, and there are sick people in at least seven other countries.

That includes two cases in the United States.

A man in his 30s in Washington state tested positive for 2019-nCoV after being hospitalized with pneumonia last week, according to a Centers…