A pathogen is a living organism or agent that can cause disease in its host. The term "pathogen" is often used to describe infectious microorganisms or agents such as viruses, bacteria, protozoa, prions, viroids, or fungi. Pathogens can also include small animals such as helminths and insects that can cause or transmit disease. Pathogenicity is the potential disease-causing capacity of pathogens, involving a combination of infectivity (pathogens ability to infect hosts) and virulence (severity of host disease) . Pathogens can cause a variety of diseases that range in severity and how they’re transmitted. The four most common types of pathogens are viruses, bacteria, fungi, and parasites. Pathogens can be transmitted through skin contact, bodily fluids, airborne particles, contact with feces, and touching a surface touched by an infected person. Preventing pathogen infections involves good hygiene practices such as washing hands regularly, cooking food thoroughly, and avoiding contact with infected individuals or animals.