Plague is an infectious disease caused by bacteria called Yersinia pestis. These bacteria are found mainly in rodents, particularly rats, and in the fleas that feed on them. Other animals and humans usually contract the bacteria from rodent or flea bites.
Historically, plague destroyed entire civilizations. In the 1300s, the "Black Death," as it was called, killed approximately one-third (20 to 30 million) of Europe's population. In the mid-1800s, it killed 12 million people in China. Today, thanks to better living conditions, antibiotics, and improved sanitation, current World Health Organization statistics show there were only 2,118 cases in 2003 worldwide.
Approximately 10 to 20 people in the United States develop plague each year from flea or rodent bites—primarily from infected prairie dogs—in rural areas of the southwestern United States. About 1 in 7 of those infected die from the disease. There has not been a case of person-to-person infection in the United States since 1924.
Worldwide, there have been small plague outbreaks in Asia, Africa, and South America.
Forms of Plague
In bubonic plague, the most common form, bacteria infect the lymph system and become inflamed. (The lymph or lymphatic system is a major component of your body's immune system. The organs within the lymphatic system are the tonsils, adenoids, spleen, and thymus.)
How do you get it?
Usually, you get bubonic plague from the bite of an infected flea or rodent. In rare cases, Y. pestis bacteria, from a piece of contaminated clothing or other material used by a person with plague, enter the body through an opening in the skin.
What are the symptoms?
Bubonic plague affects the lymph nodes (another part of the lymph system). Within 3 to 7 days of exposure to plague bacteria, you will develop flu-like symptoms such as fever, headache, chills, weakness, and swollen, tender lymph glands (called buboes—hence the name bubonic).
Is it contagious?
Bubonic plague is rarely spread from person to person.