一、人群易感性有了传染源和适宜的传播途径,没有易感者的存在,仍然不可能发生新的病例,所以易感者的存在是构成传染病流行三个环节之一,是发生新病例的必要条件。人群作为一个整体对传染病病原体容易感受的程度称为人群易感性。易感是指缺乏免疫力而言。传染病的病原体侵入人体后,由于免疫力的影响,不一定在体内生长繁殖,只确侵入缺乏免疫力的机体,才能引起传染过程的发生。这种对某种传染病病原体具有感受性的人称为该传染病的易感者。例 First, the population susceptibility With the source of infection and the appropriate route of transmission, there is no susceptible to the existence of new cases are still unlikely to occur, so the presence of susceptible constitutes an infectious disease epidemic is one of the three links is the occurrence of new Necessary conditions for the case. The extent to which a population as a whole is susceptible to a communicable disease agent is called population susceptibility. Susceptibility means lack of immunity. Infectious pathogens invade the human body, due to the impact of immunity, growth and reproduction in the body may not necessarily, invade the lack of immunity in the body, can cause the occurrence of the infection process. This kind of person who is susceptible to a certain infectious disease is called a susceptible person to the infectious disease. example