Microorganisms that are prone to cause diseases. Examples include viruses, fungi or bacteria. Usually present chemical waste, exhaust water, etc.
disease-causing microorganisms, including bacteria, fungi, and viruses, found commonly in sewage, hospital waste, run-off liquid from facilities, plus in liquid useful for swimming. Many pathogens are parasites (stay from the host) together with conditions they result are an indirect results of their getting food from, or shelter in, the host. Bigger parasites (like worms) rather than known as pathogens.
We do not call it disease when pathogens of a non-harmful or even beneficial type live in the human body.