Cowling says public health officials in China and elsewhere have two sets of tools to contain its outbreak — social distancing and case management. Social distancing makes it harder for the virus to find new people to infect. Case management tracks down cases and potential cases individually and then isolates them – and the virus. China wielded both of these tools aggressively.

“With a lot of testing capacity, they were able to bring down the numbers of infections quickly,” Cowling says. “I think more quickly than we will find case numbers decline in New York or northern Italy or Spain or France. And that’s because in China, the lockdown was a more extreme version of a lockdown. It was a total lockdown.”

People were ordered to stay in their homes and forbidden from traveling.

“In addition to the lockdown, there was also heavy use of testing, isolation and quarantine,” Cowling says. “So all of those measures are like really, really trying very hard to get the numbers down.”