A staff member distributes epidemic prevention leaflets to a passenger at Chongqingbei Railway Station in Chongqing, southwest China, Jan. 25, 2021. The prevention and control efforts against the COVID-19 epidemic are strengthened at railway stations in Chongqing to protect the safety of passengers. (Photos: Xinhua)

A staff member distributes epidemic prevention leaflets to a passenger at Chongqingbei Railway Station in Chongqing, southwest China, Jan. 25, 2021. The prevention and control efforts against the COVID-19 epidemic are strengthened at railway stations in Chongqing to protect the safety of passengers.

A police officer distributes epidemic prevention leaflets to passengers at Chongqingbei Railway Station in Chongqing, southwest China, Jan. 25, 2021. The prevention and control efforts against the COVID-19 epidemic are strengthened at railway stations in Chongqing to protect the safety of passengers.

A medical worker explains the knowledge about the COVID-19 epidemic to passengers on a train on Jan. 25, 2021. The prevention and control efforts against the COVID-19 epidemic are strengthened at railway stations in Chongqing to protect the safety of passengers.

A medical worker shows the passengers how to wash hands in seven steps on a train on Jan. 25, 2021. The prevention and control efforts against the COVID-19 epidemic are strengthened at railway stations in Chongqing to protect the safety of passengers. (Xinhua/Huang Wei)

A police officer distributes epidemic prevention leaflets to a passenger at Chongqingbei Railway Station in Chongqing, southwest China, Jan. 25, 2021. The prevention and control efforts against the COVID-19 epidemic are strengthened at railway stations in Chongqing to protect the safety of passengers.

A medical worker distributes epidemic prevention leaflets to passengers at Chongqingbei Railway Station in Chongqing, southwest China, Jan. 25, 2021. The prevention and control efforts against the COVID-19 epidemic are strengthened at railway stations in Chongqing to protect the safety of passengers.

A police officer distributes epidemic prevention leaflets to a passenger at Chongqingbei Railway Station in Chongqing, southwest China, Jan. 25, 2021. The prevention and control efforts against the COVID-19 epidemic are strengthened at railway stations in Chongqing to protect the safety of passengers.

A medical worker shows passengers how to wear facial masks correctly on a train on Jan. 25, 2021. The prevention and control efforts against the COVID-19 epidemic are strengthened at railway stations in Chongqing to protect the safety of passengers.

A staff member distributes epidemic prevention leaflets to a passenger at Chongqingbei Railway Station in Chongqing, southwest China, Jan. 25, 2021. The prevention and control efforts against the COVID-19 epidemic are strengthened at railway stations in Chongqing to protect the safety of passengers.

A medical worker explains the knowledge about the COVID-19 epidemic to passengers on a train on Jan. 25, 2021. The prevention and control efforts against the COVID-19 epidemic are strengthened at railway stations in Chongqing to protect the safety of passengers.

A staff member organizes medical supplies on a train on Jan. 25, 2021. The prevention and control efforts against the COVID-19 epidemic are strengthened at railway stations in Chongqing to protect the safety of passengers.