Wú Yànchéng 吳硯丞 was a mid-Qīng paediatric physician active in or before 1853, when his Mázhěn bèiyào fānglùn 麻疹備要方論 (KR3ej054) was printed in summer 1853 (Xiánfēng sān nián zhòngxià 咸豐三年仲夏). The preface by his apparent son Wú Yǔjiǔ 吳與九 (style Shuāngxī 雙溪) describes the work’s printing as having been organised at the time the family also published the Shénjiǔ jīnglún 神灸經綸 acupuncture-moxibustion work. The work is a sustained articulation of the doctrine that measles (mázhěn 麻疹) emerges from the yáng six fǔ and is qì-governed, in contrast to smallpox emerging from the yīn five zàng; the practical consequence is that measles is purely shírè 實熱 (replete-heat) and requires no warming treatment except in the recovery phase, where blood-nourishing is needed for the yīn-depletion that has resulted from the yáng febrile course.
No CBDB or other authoritative database entry was located for either Wú Yànchéng or Wú Yǔjiǔ; their biographical context is fixed only by the 1853 preface. They were likely Jiāngnán physicians, possibly Shànxī / Zhèjiāng region based on the social network implied by the Shénjiǔ jīnglún connection.