Plague is a disease caused by Yersinia pestis, a naturally-occurring bacterium found in many areas around the world, including the United States. There are several forms of plague, including pneumonic, bubonic, and septicemic plague.
- Pneumonic plague occurs when Y. pestis infects the lungs, and is the most deadly form of the disease. This type of plague can spread from person to person through the air. Transmission can take place if someone breathes in aerosolized bacteria, which could happen in a bioterrorist attack. Pneumonic plague is also spread by breathing in Y. pestis suspended in respiratory droplets from a person (or animal) with pneumonic plague. Direct and close contact with the ill person or animal is necessary for respiratory transmission. Pneumonic plague may also occur if a person with bubonic or septicemic plague is untreated and the bacteria spread to the lungs.
- Bubonic plague is the most common form of plague. This occurs when an infected flea bites a person or when materials contaminated with Y. pestis enter through a break in a person's skin. Patients develop swollen, tender lymph glands (called buboes) and fever, headache, chills, and weakness. Bubonic plague does not spread from person to person.
- Septicemic plague occurs when plague bacteria multiply in the blood. It can be a complication of pneumonic or bubonic plague or it can occur by itself. When it occurs alone, it is caused in the same ways as bubonic plague; however, buboes do not develop. Patients have fever, chills, prostration, abdominal pain, shock, and bleeding into skin and other organs. Septicemic plague does not spread from person to person.
The last plague epidemic in the United States occurred in Los Angeles in 1924. Since then, all human plague cases in the U.S. have been sporadic cases acquired from wild rodents or their fleas or from direct contact with plague-infected animals. The following references aid in recognizing disease characteristics and hazards associated with plague.
- Division of Vector-Borne Diseases (DVBD). Centers for Disease Control and Prevention (CDC). Provides basic disease information on plague, including a fact sheet, questions and answers, images, natural history, diagnosis, epidemiology, prevention and control, scientific literature, and more.
- Public Health Image Library (PHIL). Centers for Disease Control and Prevention (CDC). Offers several images related to plague that include descriptions.
- Plague. Centers for Disease Control and Prevention (CDC). Provides links to material on Plague Disease Topics, Plague FAQs, and other related information.
- Plague. World Health Organization (WHO) Health Topics. Provides information on plague, including a fact sheet, disease outbreak information, publications, and related links.
- WHO Report on Global Surveillance of Epidemic-prone Infectious Diseases - Chapter 3: Plague. World Health Organization (WHO), Department of Communicable Disease Surveillance and Response. Includes the background and history of plague, as well as information about disease transmission and trends.
- Current Description of Plague. The University of California Los Angeles (UCLA), Department of Epidemiology, School of Public Health. Provides basic information on plague, including identification, infectious agent, global occurrence, reservoir, mode of transmission, incubation period, communicability, susceptibility and resistance, methods of control, and more. Adapted from the Control of Communicable Diseases Manual 2000, American Public Health Association (APHA).
- Plague Manual: Epidemiology, Distribution, Surveillance and Control. World Health Organization (WHO). Provides links to PDF documents that contain the comprehensive WHO manual on plague disease.