Germs: What They Are and How They Cause Illness

Germ (rhymes with “squirm”) is a colloquial term for pathogenic microorganisms—bacteria, viruses, fungi, protozoa—that can invade the body and cause infectious disease.

They spread via direct contact, droplets, airborne particles, contaminated surfaces, vectors, or ingestion. Hygiene (handwashing, sanitation), vaccination, and antimicrobial stewardship reduce transmission and illness.