Contagion is the spread of disease from one person to another by close proximity or contact. A disease that can spread from person to person is said to be a contagious disease. SLIDESHOW Fungal Skin Infections: Types, Symptoms, and Treatments See Slideshow From Infectious Disease Resources Is It a Cold, Strep, or Tonsillitis? Featured Centers What Are the Best PsA Treatments for You?Understanding Biologics 10 Things People With Depression Wish You Knew Health Solutions From Our Sponsors Shot-Free MS Treatment Your Child and COVID-19 References Jameson, J. Larry, et al. Harrison's Principles of Internal Medicine, 20th Ed. New York: McGraw-Hill Education, 2018.