Synonyms: Germs

Medical Specialties: Family practice, Internal medicine, Preventative medicine

Clinical Definition

A pathogen is any microorganism or agent that invades another organism and causes disease or illness in its host. Pathogens are transmitted to the host via various pathways and have varying degrees of virulence.

In Our Own Words

A pathogen is any organism that can enter the body and make you sick. Pathogens can cross the threshold in different ways, such as through your digestive tract, blood, lungs, mucus membranes and cuts to the skin. Safeguards against pathogens include thorough hand washing and proper hygiene, food safety, healthy living and vaccination. After you are infected, however, a health care practitioner may recommend further use of antibiotics, antiviral medications and antifungal agents. 

Relevant Conditions
  • Upper respiratory infection
  • Gastroenteritis
  • Ebola virus
  • Influenza
Common Types
  • Bacterial
  • Parasitic
  • Fungal
  • Viral
Side Effects
  • Fever
  • Headaches (and other aches)
  • Fatigue
Share this article
  • Falkow, Stanley. “What is a Pathogen?” American Society for Microbiology News. Accessed July 2013.
  • Harvard Medical School. Medical Dictionary of Health Terms. Harvard Health Publications. Accessed July 2013.
  • International Association of Firefighters. “What is a Pathogen?” Accessed July 2013.
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