Workers make face masks at the workshop of a face mask company in Taiyuan, capital of north China's Shanxi province, Feb. 13, 2020. Face mask companies in Taiyuan have stepped up production at full speed to increase market supply amid the fight against novel coronavirus. [Photo/Xinhua]

Workers make face masks at the workshop of a face mask company in Taiyuan, capital of north China's Shanxi province, Feb. 13, 2020. Face mask companies in Taiyuan have stepped up production at full speed to increase market supply amid the fight against novel coronavirus. [Photo/Xinhua]

Workers make face masks at the workshop of a face mask company in Taiyuan, capital of north China's Shanxi province, Feb. 13, 2020. Face mask companies in Taiyuan have stepped up production at full speed to increase market supply amid the fight against novel coronavirus. [Photo/Xinhua]

Workers make face masks at the workshop of a face mask company in Taiyuan, capital of north China's Shanxi province, Feb. 13, 2020. Face mask companies in Taiyuan have stepped up production at full speed to increase market supply amid the fight against novel coronavirus. [Photo/Xinhua]

Workers make face masks at the workshop of a face mask company in Taiyuan, capital of north China's Shanxi province, Feb. 13, 2020. Face mask companies in Taiyuan have stepped up production at full speed to increase market supply amid the fight against novel coronavirus. [Photo/Xinhua]

Workers make face masks at the workshop of a face mask company in Taiyuan, capital of north China's Shanxi province, Feb. 13, 2020. Face mask companies in Taiyuan have stepped up production at full speed to increase market supply amid the fight against novel coronavirus. [Photo/Xinhua]