This did not emerge in China. And the history of the outbreak (now four days) points strongly at a release. It's also too late to contain - it has hit the whole world already. That plane is just one of many. There's two interesting factors now - the mortality rate, and can a treatment be found.
It's not clear where this came from. According to the above, the first identifiable case was an American in Vietnam, who'd been in southeastern China where there was an oubreak of "atypical pneumonia" -- though they have not proved or disproved any connection yet.