By definition, a pathogen is anything that is capable of causing disease. These include bacteria, viruses, fungi, parasites, etc.
Pathogens can enter the body through various ways:
- Through breaks in the skin. Although the skin is a great barrier to pathogens, if the skin is breached in some way (ex. cut, burn), pathogens can get in.
- Via open cavaties of the body (ex. mouth, nose, ears, eyes, vagina).