A patient (L) infected by the COVID-19 coronavirus receives acupuncture treatment at Red Cross Hospital in Wuhan in China's central Hubei province on March 11, 2020. China reported an increase in imported coronavirus cases on March 11, fuelling concerns that infections from overseas could undermine progress in halting the spread of the virus. (Photo by AFP Photo/China Stringer Network)





People wearing face masks use their phones under blooming cherry blossoms near Jiming Temple, as the country is hit by a novel coronavirus, in Nanjing, Jiangsu province, China on February 29, 2020. (Photo by Cnsphoto via Reuters)





In this March 12, 2020, photo, Chinese paramilitary policemen stand on duty behind a barrier at the Capital International Airport terminal 3 in Beijing. As the number of new cases dwindles in China and multiplies abroad, the country once feared as the source of the COVID-19 outbreak is now worried about importing cases from abroad. China hasn't imposed any travel bans, but Beijing said this week that all people arriving from overseas would have to self-quarantine for 14 days. (Photo by Ng Han Guan/AP Photo)





The Yat Tung Estate public housing stands in Tung Chung, Hong Kong, China, 15 March 2020. Tung Chung is located on ​Lantau Island, a few kilometres away from Hong Kong International Airport. (Photo by Jérôme Favre/EPA/EFE)





A man wearing a protective face mask walks by a propaganda poster promoting to protect wildlife animals after authorities crackdowns on wild animal markets following the coronavirus outbreak in Beijing, Wednesday, March 11, 2020. For most, the coronavirus causes only mild or moderate symptoms, such as fever and cough. But for a few, especially older adults and people with existing health problems, it can cause more severe illnesses, including pneumonia. (Photo by Andy Wong/AP Photo)





A woman places food out on a balcony to dry at a residential compound in Wuhan, the epicenter of the coronavirus outbreak, Hubei province, China, March 10, 2020. (Photo by Reuters/China Stringer Network)





Junior high students wearing face masks attend a class on their first day of returning to school following an outbreak of coronavirus, in Guiyang, Guizhou province, China on March 16, 2020. (Photo y Cnsphoto via Reuters)





A man wears a protective face mask at a butcher shop following an outbreak of coronavirus disease (COVID-19), in downtown Shanghai, China on March 16, 2020. (Photo by Aly Song/Reuters)





A man wearing a face mask lies on an exercise machine at a park, as the country is hit by an outbreak of the novel coronavirus, in Shanghai, China on March 11, 2020. (Photo by Aly Song/Reuters)





People wearing face masks walk at a street in Hong Kong Friday, March 13, 2020. For most, the coronavirus causes only mild or moderate symptoms, such as fever and cough. But for a few, especially older adults and people with existing health problems, it can cause more severe illnesses, including pneumonia. (Photo by Vincent Yu/AP Photo)





An employee wears a face mask as she waits for customers at a meat stall at a market in Beijing, Saturday, March 14, 2020. The United States declared a state of emergency Friday as many European countries went on a war footing amid mounting deaths as the world mobilized to fight the widening coronavirus pandemic. For most people, the new coronavirus causes only mild or moderate symptoms, such as fever and cough. For some, especially older adults and people with existing health problems, it can cause more severe illness, including pneumonia. (Photo by Mark Schiefelbein/AP Photo)





A man wearing a face mask walks on a downtown street in Hong Kong Monday, March 16, 2020. For most, the coronavirus causes only mild or moderate symptoms, such as fever and cough. But for a few, especially older adults and people with existing health problems, it can cause more severe illnesses, including pneumonia. (Photo by Vincent Yu/AP Photo)





Chinese paramilitary wearing masks form up during their duty in an embassy district in Beijing on Monday, March 16, 2020. With more imported cases of the new coronavirus, starting Monday, travelers arriving in Beijing from overseas will be quarantined for 14 days in designated facilities at their own expense. For most people, the new coronavirus causes only mild or moderate symptoms. For some it can cause more severe illness. (Photo by Ng Han Guan/AP Photo)





In this Tuesday, February 4, 2020 file photo, a member of an honor guard wears a face mask as he stands guard in Tiananmen Square in Beijing. On Wednesday, March 17, 2020, China announced that it will revoke the media credentials of American journalists at three major U.S. news organizations, in effect expelling them from the country, in response to new U.S. restrictions on Chinese state-controlled media. (Photo by Mark Schiefelbein/AP Photo)





A woman wipes the face of a child on the streets of Beijing on Thursday, March 12, 2020. For most people, the new coronavirus causes only mild or moderate symptoms. For some it can cause more severe illness, especially in older adults and people with existing health problems. (Photo by Ng Han Guan/AP Photo)





A bus is disinfected with ultraviolet rays as part of measures against of the COVID-19 coronavirus in Shanghai on March 12, 2020 (Photo by Hector Retamal/AFP Photo)





A medical worker walks by the oxygen canisters in a hospital designated for COVID-19 patients in Wuhan in central China's Hubei province Wednesday, March 11, 2020. (Photo by Feature China/Barcroft Media via Getty Images)





Passengers wearing face masks wait for their train at Changsha railway station in Changsha, China's central Hunan province on March 10, 2020. Chinese President Xi Jinping arrived in Wuhan on March 10 for his first visit to the epicentre of the coronavirus epidemic since the crisis erupted in January – a major sign that officials believe the outbreak is under control. (Photo by Noel Celis/AFP Photo)





People wearing masks dance at a park in Beijing, China, 13 March 2020. The World Health organization (WHO) officially declared the coronavir​us outbreak a pandemic on 11 March 2020. (Photo by Wu Hong/EPA/EFE)





A villager attends a spring ploughing ceremony in Jiaru Village, Gurong Town, Lhasa, southwest China's Tibet Autonomous Region, March 16, 2020. Traditional spring ploughing ceremonies took place in Tibet's major cultivation areas on Monday to pray for a year with good harvests. (Photo by Zhan Yan/Xinhua News Agency)