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    Virus

    Virus

    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 22, 2015

    Author: Healthwise Staff

    Medical Review: E. Gregory Thompson, MD - Internal Medicine & Christine Hahn, MD - Epidemiology

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