In recent days, though, Beijing seems to be reasserting its primacy over information in ways that go beyond mere rumor control. At a meeting this past weekend between Mr. Xi and other senior leaders, one of the measures they resolved to take against the virus was to “strengthen the guidance of public opinion.”

Wang Huning, the head of the Communist Party’s publicity department and an influential party ideologue, was also recently named deputy head of the team in charge of containing the outbreak, behind only China’s premier, Li Keqiang.

Chinese officials seem to recognize that social media can be a useful tool for feeling out public opinion in times of crisis. WeChat, the popular Chinese messaging platform, said over the weekend that it would crack down hard on rumors about the virus. But it also created a tool for users to report tips and information about the disease and the response.

Internet backlash may already have caused one local government in China to change course on its virus-fighting policies. The southern city of Shantou announced on Sunday that it was stopping cars, ships and people from entering the city, in a policy that echoed ones in Wuhan. But then word went around that the decision had led people to panic-buy food, and by the afternoon, the order had been rescinded.