微生物侵入动物或人体,因而发生疾病就叫传染。凡侵入人体或动物体能引起病变之细菌称为病原菌。人和动物体外周围的环境都有许多病原菌存在,可是不一定会引起传染,是否会传染,这与病原菌本身,宿主的抵抗力及周围之环境,如温度、病媒等,都有关系。 Microorganisms invade the animal or human body, so the disease is called infection. Any invade the human or animal body can cause lesions of bacteria called pathogens. There are many pathogenic bacteria exist in the environment around humans and animals in vitro. However, it does not necessarily cause infection or contagion. It is related to the pathogen itself, the host’s resistance and the surrounding environment, such as temperature and vector.