A Chinese national flag flies at half-mast to mourn for martyrs who died in the fight against the novel coronavirus disease (COVID-19) outbreak and compatriots who died of the disease at Tian'anmen Square in Beijing, capital of China, April 4, 2020. (Xinhua/Ju Huanzong)

A Chinese national flag flies at half-mast to mourn for martyrs who died in the fight against the novel coronavirus disease (COVID-19) outbreak and compatriots who died of the disease at Tian'anmen Square in Beijing, capital of China, April 4, 2020. (Xinhua/Peng Ziyang)

A Chinese national flag flies at half-mast to mourn for martyrs who died in the fight against the novel coronavirus disease (COVID-19) outbreak and who compatriots died of the disease at Tian'anmen Square in Beijing, capital of China, April 4, 2020. (Xinhua/Ju Huanzong)

A Chinese national flag flies at half-mast to mourn for martyrs who died in the fight against the novel coronavirus disease (COVID-19) outbreak and compatriots who died of the disease at Tian'anmen Square in Beijing, capital of China, April 4, 2020. (Xinhua/Ju Huanzong)