Fact sheet N°267
Updated November 2014
Plague is an infectious disease caused by the bacteriaYersinia Pestis, a zoonotic bacteria, usually found in small animals and their fleas. It is transmitted between animals and humans by the bite of infected fleas, direct contact, inhalation and rarely, ingestion of infective materials.
Plague can be a very severe disease in people, with a case-fatality ratio of 30%-60% if left untreated. In 2013 there were 783 cases reported worldwide, including 126 deaths. Historically, plague was responsible for widespread pandemics with high mortality. It was known as the "Black Death" during the fourteenth century, causing an estimated 50 million deaths, approximately half of them in Asia and Africa and the other half in Europe, where a quarter of the population succumbed.
People infected with plague usually develop “flu-like” symptoms after an incubation period of 3-7 days. Typical symptoms are the sudden onset of fever, chills, head and body-aches and weakness, vomiting and nausea.
There are 3 forms of plague infection, depending on the route of infection: bubonic, septicaemic and pneumonic.
Plague is endemic in many countries in Africa, the former Soviet Union, the Americas and Asia. The distribution of plague coincides with the geographical distribution of the rodents it infects, which are found in all continents except Australia, within a broad belt in tropical, subtropical and warmer temperate climates. Plague epidemics have occurred in Africa, Asia, and South America but since the 1990s, most human cases have occurred in Africa. The 3 most endemic countries are Madagascar, the Democratic Republic of Congo and Peru.
Diagnosis and confirmation of plague requires laboratory testing. The best way to confirm that a patient has plague is to identifyY Pestis in a sample of fluid from a bubo, or blood or sputum. Rapid dipstick tests have been validated for field use to quickly screen forY. pestis antigen in patients. Specimens should be collected and forwarded to laboratories for plague testing.
Untreated plague can be rapidly fatal so early diagnosis and treatment is essential for survival and reduction of complications. Antibiotics and supportive therapy are effective against plague if patients are diagnosed in time. These methods include the administration of antibiotics and supportive therapy.
Preventive measures include informing people when zoonotic plague is active in their environment and advising them to take precautions against flea bites and not to handle animal carcasses in plague-endemic areas. People should also avoid direct contact with infected tissues such as suppurating buboes, or exposure to patients with pneumonic plague.
Plague vaccines were once widely used but have not been shown to be very effective against plague. Vaccines are currently not recommended during outbreaks but are still used for high-risk groups (e.g. laboratory personnel who are constantly exposed to the risk of contamination).
Surveillance and control requires investigating animal and flea species implicated in the plague cycle in the region and developing environmental management programmes to limit spread. Active long-term surveillance of animal foci, coupled with a rapid response during animal outbreaks has successfully reduced numbers of human plague outbreaks.
