预防医学的三级机构是六十年代美国一些学者所提出。它的内容是:一级预防(病因性预防),是最重要最积极的预防,它注重病因学的综合性研究,找出防范办法,制订有效预防措施;二级预防(发病性预防),主要内容是尽可能早地发现患病者,把握、鉴别疾病发生前驱期与潜伏期迹象,建立高度可靠的疾病监测系统,采取得力措施不让 The third class of preventive medicine was proposed by some American scholars in the 1960s. Its content is: Primary prevention (prevention of etiology) is the most important and active prevention. It focuses on a comprehensive study of etiology to find out the precautionary measures and formulate effective preventive measures. Secondary prevention (prevention of onset) The main content is to find the sick as soon as possible, grasp, identify signs of pre-illness and incubation period, establish a highly reliable disease surveillance system, take effective measures to prevent