A virus is a microscopic organism that causes infection and disease. Viral illnesses can range from mild to severe. Some examples are the common cold, West Nile virus, polio, and smallpox.
Current as of: May 24, 2016
Author: Healthwise Staff
Medical Review: E. Gregory Thompson, MD - Internal Medicine & Adam Husney, MD - Family Medicine & Christine Hahn, MD - Epidemiology
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