Passengers walk to board their train at the Beijing Railway Station, in Beijing, capital of China, Jan. 28, 2021. The Spring Festival travel rush, known as the world's largest annual human migration, lasts 40 days from Jan. 28 to March 8 this year. (Photos: Xinhua)

Passengers place their luggage on the overhead rack on the train 3603 from Beijing to Chongqing, in Beijing, capital of China, Jan. 28, 2021. The Spring Festival travel rush, known as the world's largest annual human migration, lasts 40 days from Jan. 28 to March 8 this year.

A passenger walks through the infrared temperature measuring area when entering the Beijing Railway Station in Beijing, capital of China, Jan. 27, 2021. The Spring Festival travel rush, known as the world's largest annual human migration, lasts 40 days from Jan. 28 to March 8 this year.

A train driver makes preparations before departure on the train 3603 from Beijing to Chongqing, in Beijing, capital of China, Jan. 28, 2021. The Spring Festival travel rush, known as the world's largest annual human migration, lasts 40 days from Jan. 28 to March 8 this year.

Passengers wait to check in at the Beijing Railway Station, in Beijing, capital of China, Jan. 28, 2021. The Spring Festival travel rush, known as the world's largest annual human migration, lasts 40 days from Jan. 28 to March 8 this year.

Passengers walk to board their train at the Beijing Railway Station, in Beijing, capital of China, Jan. 28, 2021. The Spring Festival travel rush, known as the world's largest annual human migration, lasts 40 days from Jan. 28 to March 8 this year.

The train 3603 from Beijing to Chongqing parks at the Beijing Railway Station, in Beijing, capital of China, Jan. 28, 2021. The Spring Festival travel rush, known as the world's largest annual human migration, lasts 40 days from Jan. 28 to March 8 this year.

A staff member sprays disinfectant at the Beijing Railway Station, in Beijing, capital of China, Jan. 27, 2021. The Spring Festival travel rush, known as the world's largest annual human migration, lasts 40 days from Jan. 28 to March 8 this year.

A staff member makes final inspections before the train 3603 departs from Beijing to Chongqing, in Beijing, capital of China, Jan. 28, 2021. The Spring Festival travel rush, known as the world's largest annual human migration, lasts 40 days from Jan. 28 to March 8 this year.

A staff member sprays disinfectant at the Beijing Railway Station, in Beijing, capital of China, Jan. 27, 2021. The Spring Festival travel rush, known as the world's largest annual human migration, lasts 40 days from Jan. 28 to March 8 this year.

Passengers get ready to depart on the train 3603 from Beijing to Chongqing, in Beijing, capital of China, Jan. 28, 2021. The Spring Festival travel rush, known as the world's largest annual human migration, lasts 40 days from Jan. 28 to March 8 this year.

A crew member checks tickets on the train 3603 from Beijing to Chongqing, in Beijing, capital of China, Jan. 28, 2021. The Spring Festival travel rush, known as the world's largest annual human migration, lasts 40 days from Jan. 28 to March 8 this year.

A Staff member talks through a loudspeaker about epidemic prevention precautions in the waiting hall of Hankou Raiway Station in Wuhan, central China's Hubei Province, Jan. 28, 2021. The Spring Festival travel rush, known as the world's largest annual human migration, lasts 40 days from Jan. 28 to March 8 this year.

A passenger sits in the waiting hall of Changchun Railway Station in Changchun, northeast China's Jilin Province, Jan. 28, 2021. The Spring Festival travel rush, known as the world's largest annual human migration, lasts 40 days from Jan. 28 to March 8 this year.

A passenger wearing a protective suit waits to check in at the waiting hall of Changchun Railway Station in Changchun, northeast China's Jilin Province, Jan. 28, 2021. The Spring Festival travel rush, known as the world's largest annual human migration, lasts 40 days from Jan. 28 to March 8 this year.

A bullet train enters Shenyang North Railway Station in Shenyang, northeast China's Liaoning Province on Jan. 28, 2021. The Spring Festival travel rush, known as the world's largest annual human migration, lasts 40 days from Jan. 28 to March 8 this year.

A volunteer helps a kid put on a face mask at Kaili South Railway Station in southwest China's Guizhou Province, Jan. 28, 2021. The Spring Festival travel rush, known as the world's largest annual human migration, lasts 40 days from Jan. 28 to March 8 this year.

A staff member helps a passenger scan the health tracking QR code before entering Kaili South Railway Station in southwest China's Guizhou Province, Jan. 28, 2021. The Spring Festival travel rush, known as the world's largest annual human migration, lasts 40 days from Jan. 28 to March 8 this year.

A passenger walks to board the train at Hefei South Railway Station in Hefei, east China's Anhui Province, Jan. 28, 2021. The Spring Festival travel rush, known as the world's largest annual human migration, lasts 40 days from Jan. 28 to March 8 this year.

A staff member drives a cleaning vehicle to clean the waiting hall of Fuzhou Railway Station in Fuzhou, southeast China's Fujian Province, Jan. 28, 2021. The Spring Festival travel rush, known as the world's largest annual human migration, lasts 40 days from Jan. 28 to March 8 this year.