A Chinese tourist wears a mask as she arrives at Suvarnabhumi Airport during a welcome ceremony of Chinese Lunar New Year travellers in Bangkok, Thailand January 22, 2020. REUTERS/Soe Zeya Tun

Passengers wearing masks are seen at the waiting area for a train to Wuhan at the Beijing West Railway Station, ahead of the Chinese Lunar New Year, in Beijing, China January 20, 2020. REUTERS/Stringer

A man pushes his luggage as a child sits atop with a mask at the Beijing West Railway Station, ahead of Chinese Lunar New Year, in Beijing, China January 20, 2020. REUTERS/Stringer

A woman holding a rat stuffed toy sits inside a train as the annual Spring Festival travel rush begins ahead of the Chinese Lunar New Year, at a railway station in Beijing, China January 10, 2020. REUTERS/Jason Lee

Travellers wait for their train at a railway station as the annual Spring Festival travel rush begins ahead of the Chinese Lunar New Year, in Beijing, China January 10, 2020. REUTERS/Jason Lee

A boy takes a nap in a train as the annual Spring Festival travel rush begins ahead of the Chinese Lunar New Year, in Shijiazhuang, Hebei province, China January 10, 2020. Picture taken January 10, 2020. REUTERS/Jason Lee

Chinese tourists wear masks as they arrive at Suvarnabhumi Airport during a welcome ceremony of Chinese Lunar New Year travellers in Bangkok, Thailand January 22, 2020. REUTERS/Soe Zeya Tun

A woman wearing a mask is seen at a waiting area for a train to Wuhan at the Beijing West Railway Station, ahead of Chinese Lunar New Year, in Beijing, China January 20, 2020. REUTERS/Stringer

Passengers wearing masks walk under a train information board at the Beijing West Railway Station, ahead of the Chinese Lunar New Year, in Beijing, China January 20, 2020. REUTERS/Stringer

People walk outside Beijing Railway Station during the annual Spring Festival travel rush ahead of the Chinese Lunar New Year, in Beijing, China January 20, 2020. REUTERS/Carlos Garcia Rawlins

Travellers line up to board their train at a railway station as the annual Spring Festival travel rush begins ahead of the Chinese Lunar New Year, in Shijiazhuang, Hebei province, China January 10, 2020. REUTERS/Jason Lee TPX IMAGES OF THE DAY

An employee stands behind a door as the train arrives at a railway station while the annual Spring Festival travel rush begins ahead of the Chinese Lunar New Year, in Baoding, Hebei province, China January 10, 2020. Picture taken January 10, 2020. REUTERS/Jason Lee

A traveller pushes his luggage as his son rides atop, in Beijing West Railway Station during the annual Spring Festival travel rush ahead of the Chinese Lunar New Year, in Beijing, China January 13, 2020. Picture taken January 13, 2020. REUTERS/Jason Lee TPX IMAGES OF THE DAY

Travellers wait for their trains inside Zhengzhou East Railway Station during the annual Spring Festival travel rush ahead of the Chinese Lunar New Year, in Zhengzhou, Henan province, China January 13, 2020. Picture taken January 13, 2020. REUTERS/Jason Lee

A father feeds water to his son next to his daughter in a train during the annual Spring Festival travel rush ahead of the Chinese Lunar New Year, in Luohe, Henan province, China January 14, 2020. Picture taken January 14, 2020. REUTERS/Jason Lee

Travellers wait for their train at a railway station as the annual Spring Festival travel rush begins ahead of the Chinese Lunar New Year, in Beijing, China January 10, 2020. REUTERS/Jason Lee

A passenger wears a mask at Shanghai railway station in Shanghai, China January 22, 2020. REUTERS/Aly Song

Paramilitary police officers wearing masks are seen at Shanghai railway station in Shanghai, China January 22, 2020. REUTERS/Aly Song

Passengers wearing masks are seen on a train at Shanghai railway station in Shanghai, China January 21, 2020. REUTERS/Aly Song

Passengers wearing masks are seen at Hongqiao International Airport in Shanghai, China January 20, 2020. REUTERS/Aly Song

Performers wear costumes for the arrival of Chinese tourists at Suvarnabhumi Airport during a welcome ceremony of Chinese Lunar New Year travellers in Bangkok, Thailand January 22, 2020. REUTERS/Soe Zeya Tun

A child wears mask to prevent an outbreak of a new coronavirus at the Hong Kong West Kowloon High Speed Train Station, in Hong Kong, China January 23, 2020. REUTERS/Tyrone Siu TPX IMAGES OF THE DAY