许多人都有他们自己对于感染的定义,但医科学生常常因为不能区别定居、感染和疾病而感到为难。学生的这种烦恼,姑且不提比他们年长者的不安心情,恐怕反映了某种程度的看法不统一,因为给感染下定义和解释发病机理并不是容易的。将某一个病原体与某一种疾病直接联系起来,这种做法保险可靠,如伤寒沙门氏菌与伤寒,A群链球菌与猩红热,大叶性肺炎与肺炎球菌,但是即使在这一小类疾病中, Many people have their own definition of infection, but medical students often feel embarrassed because they can not distinguish between colonization, infection and illness. This worry of students, let alone mentioning the anxiety of their senior citizens, probably reflects some degree of disagreement because it is not easy to define and explain the pathogenesis of infection. It is safe to link a particular pathogen to a particular disease, such as Salmonella typhi and typhoid fever, group A streptococci and scarlet fever, lobar pneumonia and pneumococcal disease, but even in this subgroup of diseases,