Wu developed surgical masks into more substantial masks with layers of gauze and cotton to filter the air.[13][14] Gérald Mesny, a prominent French doctor, who had come to replace Wu, refused to wear a mask and died days later of the plague.[12][13][4] The mask was widely produced, with Wu overseeing the production and distribution of 60,000 masks in a later epidemic, and it featured in many press images.[15][13] It is believed that the N95 mask is the descendant of Wu's design.[16]

Chen took the Trans-Siberian Railroad, and shared the journey with Wu Lien-te, a physician born in Malaysia. Learning that Chen had no Chinese name, Wu suggested "Youren" as the equivalent of "Eugene": "Youren" has the meaning of "friend of benevolence", and thus echoed his birth name both in meaning and (especially when pronounced in Cantonese) sound.