WebMD
Font Size
A
A
A

Virus

A virus is a microscopic organism that causes infection and disease. Viral illnesses can range from mild to severe, including examples such as the common cold, West Nile virus, polio, and smallpox.

Author Maria G. Essig, MS, ELS
Editor Susan Van Houten, RN, BSN, MBA
Associate Editor Pat Truman, MATC
Primary Medical Reviewer Kathleen Romito, MD - Family Medicine
Specialist Medical Reviewer W. David Colby IV, MSc, MD, FRCPC - Infectious Disease
Last Updated July 31, 2008

WebMD Medical Reference from Healthwise

Last Updated: July 31, 2008
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.
© 1995-2008 Healthwise, Incorporated. Healthwise, Healthwise for every health decision, and the Healthwise logo are trademarks of Healthwise, Incorporated.