本文以現存中國第一本病因、病理與證候學專論《諸病源候論》(610) 為中心，輔以魏晉至隋唐時期其他醫學典籍，深入採究醫者如何認識與分類傳染性疾疫，與建立相關的病因學理論。本文發現，魏晉至階唐時期的醫者確有疾疫相染的觀念，然而，疾疫相染易與否並非疾病分類主要的標準。《諸病源候論》對於疾病病因的理解，傾向於「一候 (病) 多源」，以為疾疫相染的原因，或由於外在力量，抑或導源於內外交迫，或失之於飲食與勞倦等等，不止一端。雖然《諸病源候論》建立相當系統化的醫學理論，嘗試詮釋與掌握能相染易的疾疫之病因及其相染與傳播之途徑，但值得注意的是，作者在字千里行間透露出其中仍有若干隱晦或不確定的因素。 本文在研究方法上，既不以現代生物醫學為標準而解講古代文獻，亦不以現代醫學為準則而批判或表彰古人的醫學成就。本文強調將醫學典籍還原因其歷史情境中，審慎分析其內容、脈絡及其與當代思潮之間的互動關係。 本文在研究過程中，特意分別呈現醫者與一般人對於能相染疾疫的病源與相染途徑之見解，互相對照，以突顯不同專業與身分之間的異同，並藉此觀察疾病、醫學與社會之動態聯繫。 魏晉至隋唐之間，政治與社會動盪的原因之一，殆因疾疫迭起。世人除了傷逝之外，普遍相信疾疫相染與鬼物致病，遂有逃疫遷徙與棄置親人之舉，以及畏懼歸煞、驅疫厭勝與立祠崇拜之事，而與當世孝義精神與倫理價值有所齟齬，凡此種種，均不斷加深社會對於疾疫的集體焦慮。醫者身處其間，一方面做營生立命之圖，建立專業的醫學理論；另一方面則心存悲憫，提供醫療服務與預防方法，神益當世。醫者建構的疾疫相染觀念與相關理論，不論是賡續前代醫學，或融入醫者的敏銳觀察，均能反映當時社會思想與文化的若干基調。

This paper examines the Zhubing yuanhou lun (The Origins and Symptoms of Disorders, 610), the earliest extant Chinese medical text centering on aetiology and symptoms of disease, along with many other medical accounts, to explore contemporaneous Chinese conceptions and doctrines of contagion, origins, and agents of contagious disease. Un1ike most previous studies, which apply modem biological medicine as the only criterion by which to judge and evaluate Chinese medicine, this study focuses on a single medical text and analyzes its place within its historical, social and cultural contexts. This paper points out the risk and confusion that result from adopting modem medical jargon and theory to study pre-modem Chinese medicine. Moreover, I also set out to examine the medical expert’s and the layman’s respective ideas of origins of contagious disease in order to contrast different professions and social status. Furthermore, this paper delves into the moral dilemma inherent in f1eeingepidemics: on the one hand is the notion of self-preservation, on the other hand lies the responsibility of helping family members. Social debates about such choices, embedded within political, intellectual and social concerns and anxiety, provide a closer look into the social history of medieval China.