Yersinia Pestis Bacteria
When a Yersinia pestis infection is suspected, the patient is hospitalized and placed in isolation. Treatment is started even before lab tests come back, usually involving antibiotics. It is important that people who have been in close contact with a plague patient, particularly a patient with plague pneumonia, be identified and evaluated.
Left untreated, Yersinia pestis bacteria can quickly multiply in the bloodstream, causing septicemic plague, or even progress to the lungs, causing pneumonic plague. When treatment is started early, the plague morality rate is only 15 percent; however, if the infection is left untreated, the mortality rate is 50 to 90 percent.
It is probable that wild rodent hosts will continue to carry the Yersinia pestis bacteria, and the organism will most likely continue to exist in its many localized geographic areas around the world. Attempts to eliminate wild rodent plague are costly and futile; therefore, plague prevention is aimed at reducing the threat of infection in humans in high-risk areas through three techniques:
- Preventive drug therapy
- Environmental management
- Public health education.
Approximately 10 to 20 people in the United States develop Yersinia pestis infections each year. In rural areas of the Southwestern United States, these infections are most often acquired through the bites of infected prairie dogs. About one in seven of those infected die as a result. There has not been a case of person-to-person infection in the United States since 1924.
Outbreaks generally tend to occur in Asia, Africa, and South America. Globally, the World Health Organization (WHO) reports 1,000 to 3,000 cases of Yersinia pestis infections every year. Current WHO statistics show there were 2,118 cases in 2003 worldwide.
Plague occurs more frequently in males and in people under the age of 20. It is also more common in the spring and summer months.
(Click Where Is Plague? for more information.)