Text this number to tell the Chinese authorities everywhere you’ve been recently.

To combat the spread of the coronavirus, Chinese officials are using a combination of technology and policing to track movements of citizens who may have visited Hubei Province.

Mobile phone owners in China get their service from one of three state-run telecommunications firms, which this week introduced a feature for subscribers to send text messages to a hotline that generates a list of provinces they have recently visited.

That has created a new way for the authorities to see where citizens have traveled.

At a high-speed rail station in the eastern city of Yiwu on Tuesday, officials in hazmat suits demanded that passengers send the text messages and then show their location information to the authorities before being permitted to leave the station. Those who had passed through Hubei were unlikely to be allowed entry.

Other cities were taking similar measures.

Companies in China generally shy away from sharing location data with the local authorities, over fears it could be leaked or sold. And there were some signs that the companies were uncomfortable with the new rule.