not present at the time of admission (25%)
•病：urinary tract, respiratory, wound, skin, soft tissue, septicaemia
•preventable—medical& nursing & surgical不洗手，咳嗽, intravenous access静脉注射；urinary catheters尿导，surgeries
•non-preventable—不能控制的can’t control：免疫力低下，器官损伤，枪伤
•传染途径：
-environment,
-person to person (endogenous, exogenous),
-food supply
-air supply
-fomites
-vector
-water supply
•3 factors transmission chain:
source-replicate & disseminate; do:pest control, precautions, detection & identification of source.
route of infection-get to host; done: sterilize, disinfect, aseptic techniques, ventilation, food & water supply.
host-how susceptible (age, immune..); do: asepsis, vaccines, isolation/quarantine.
阻止传播链：
使源无感染性；防止微生物离开源；
干扰传播途径；
防止微生物进入宿主
最有效的—identification & detection of the source of infection