He expanded on surgical masks he had seen in the West, developing them into more substantial masks with layers of gauze and cotton to filter the air through its several layers of cloth.



The mask wrapped securely around one's face. Some doctors, however, still doubted the effectiveness of Dr Wu's face masks, with one such doctor dying of the plague after refusing to wear the mask.



According to the National Library of Medicine paper, his name was Gérald Mesny. He was a prominent French doctor who had come to replace Dr Wu. He doubted Dr Wu's views and refused to wear the mask.



"Wu explains to the French doctor his theory that the plague is pneumonic and airborne. And the French guy humiliates him. And to prove this point, Mesny goes and attends the sick in a plague hospital without wearing Wu's mask, and he dies in two days with the plague," Lynteris told Fast Company.



Prior to refusing to wear Wu's mask, Mesny said: "What can we expect from a Chinaman?"