These are collectively called pathogens. So the whole point of the immune system is, on a first line of defense, keep these things out-- and then if they were to get into your body, to kill and eliminate them from our system so that we don't get sick and so that we don't die.
เราเรียกสิ่งเหล่านี้รวมกันว่า pathogen (แพ-เทอะ-เจิ้น) หรือ ตัวก่อโรค