About Plague

Key points

• Plague is a potentially life-threatening disease caused by the bacterium Yersinia pestis.
• Plague is spread to people through bites from infected rodent fleas or, less often, direct contact with an infected animal.
• Plague occurs naturally in parts of the western United States. Sudden illness or death among wild rodents, such as squirrels or prairie dogs, could indicate plague activity.
• Plague can be cured with antibiotics, but treatment must be given quickly.

Overview

Plague is a disease that affects humans and other mammals. It is caused by the bacterium, Yersinia pestis. People usually become infected through the bite of an infected rodent flea or by handling an infected animal. Plague can be cured with antibiotics, but these must be given promptly to prevent serious illness or death. Plague is infamous for killing millions of people in Europe during the Middle Ages. Nowadays, it is a rare but persistent cause of illness in rural areas in the western United States and certain regions of Africa and Asia.

Aug. 24, 2026

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National Center for Emerging and Zoonotic Infectious Diseases (NCEZID)About This Page

Published: May 15, 2024

Updated: August 24, 2026This page was last updated on this date. Updates may include minor edits, image changes, or other modifications to page content.

Reviewed: August 24, 2026The information on this page was last reviewed by subject matter experts to ensure accuracy.

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