Chinese authorities are testing millions of people, imposing lockdowns and shutting down schools after multiple locally transmitted coronavirus cases were discovered in three cities across the country last week, AP reported.

As temperatures drop, widescale measures are being enacted in Tianjin, Shanghai and Manzhouli, even though the number of new cases remains low compared to the United States and other countries that are seeing new waves of infections.

Experts and government officials have warned that the chance of the virus spreading will be greater in cold weather. Recent flareups have shown that there is still a risk of the virus returning, despite being largely controlled within China.