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Plague still occurs in the world today, but outbreaks are rare. Bubonic plague, the most common, results in "buboes" or swelling at the lymph glands. Fortunately, antibiotics are effective at treating plague.

Information for Health Professionals

Plague is a bacterial zoonotic disease (a disease we get from animals), caused by the bacterium Yersinia pestis. It can result in three forms of disease: bubonic plague, pneumonic plague and septicemic plague. Over the centuries, plague has killed over 200 million people, but today, outbreaks from plague are rare. 

Plague still occurs in parts of Africa, southeastern Europe, Asia and the Americas. In the US, 10 to 15 cases occur each year, in the Southwest. In 2007, over 2,000 cases were reported worldwide, with over 99 per cent of these occurring in Africa, and about half of these in the Democratic Republic of Congo.


The reservoir, or source of the Yersinia pestis bacteria is infected rodents primarily. When fleas bite an infected rodent and then bite a person, infection can occur. 

Bubonic plague involves the lymph nodes and is the most common form. Inhalation of the bacteria can cause pneumonic plague, and septicemia (blood poisoning) can result from both forms. Plague can also be caused by contact with the body fluids and respiratory secretions of infected individuals. In some instances, direct contact with household cats and rabbits that have been infected can cause disease.


The early symptoms of all forms of plague include:

  • Fever
  • Chills
  • Muscle pain
  • Weakness
  • Headache, and can include
  • Nausea
  • Vomiting
  • Diarrhea, and
  • Abdominal pain

Incubation period is generally one to seven days; plague pneumonia may take less than one day, and up to four days, to incubate.


Tests to diagnose plague include:

  • Microscopic identification of the pathogen in infected body fluids
  • Identification of antibodies by ELISA or FA (fluorescent antibody) tests
  • Identification of Y. pestis antigens

Treatment must begin as early in the stages of disease as possible, and includes antibiotics.  


The fatality rate of untreated bubonic plague is 50 to 60 per cent. Untreated pneumonic or septicemic plague is almost always fatal.


There is a vaccine for specific personnel who may be at heightened risk of infection. However, the vaccine can have significant side effects and is not available for the general public. 

Flea eradication, and then rodent control is essential, especially in endemic areas. Also, appropriate precautions around infected body fluids with bubonic plague, and respiratory discharges around individuals with plague pneumonia are required to prevent the spread of this disease, until at least 48 hours after the administration of antibiotics. Veterinary staff working with potentially infected animals should also take appropriate contact precautions.

Control of Communicable Diseases Manual, Heymann, 2008


Last Updated: May 7, 2012

SOURCE: Plague ( )
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