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Plague is a bacterial zoonosis caused by Yersinia pestis, usually found in fleas and small rodents that constitute the reservoir of the disease. It is transmitted to humans by flea bite, contact with rodents or inhalation of infected droplets. There are three clinical forms: bubonic plague, pulmonary plague and septicemic plague. The usual presentation is a flu-like syndrome possibly accompanied by an inflammatory lymphadenopathy which appears after 1 to 7days of incubation. Bubonic plague has a case fatality rate of about 50% while other forms of plague are almost always fatal without treatment. Diagnosis can be confirmed by usual bacteriological techniques (Gram examination, culture) but also by serological examination, use of rapid diagnostic tests or PCR. Although aminoglycosides are traditionally regarded as the most effective treatment, fluoroquinolones or cyclins are currently recommended in France. Plague is one of the re-emerging diseases according to the WHO and Madagascar suffered in 2017 the most important plague epidemic of the 21st century with more than 2000 cases and 200 deaths. Peru and the Democratic Republic of Congo are also considered endemic areas. Public health measures and a relentless fight against poverty are the cornerstone of the control of the disease. Vaccine improvement in endemic areas may also play an important role.


People who have the plague usually develop flu-like symptoms two to 6 days after infection. There are other symptoms that can help distinguish the three forms of the plague.

Bubonic plague symptoms

Symptoms of bubonic plague generally appear within two to 8 days of infection. They include:

fever and chills


muscle pain

general weakness

You may also experience painful, swollen lymph glands, called buboes. These typically appear in the groin, armpits, neck, or site of the insect bite or scratch. The buboes are what give the bubonic plague its name.

Septicemic plague symptoms

Septicemic plague symptoms usually start within a few days after exposure, but septicemic plague can lead to death before symptoms even appear. Symptoms can include:

abdominal pain


nausea and vomiting

fever and chills

extreme weakness

bleeding (blood may not be able to clot)


skin turning black (gangrene)

Pneumonic plague symptoms

Pneumonic plague symptoms may appear as quickly as one day after exposure to the bacteria. These symptoms include:

trouble breathing

chest pain




overall weakness

bloody sputum (saliva and mucus or pus from the lungs)


Bubonic plague is a type of infection caused by the Yersinia pestis (Y. pestis) bacterium which is spread mostly by fleas on rodents and other animals. Humans who are bitten by the fleas then can come down with plague. It’s an example of a disease that can spread between animals and people (a zoonotic disease).

It can be noted that cats in particular are vulnerable to plague and can be infected by eating sick rodents. These cats can pass droplets infected with plague to their owners or to the veterinarians that treat them.

Person-to-person spread is unlikely, except in rare cases of someone who has pneumonic plague (infected lungs) spreading plague through droplets sprayed into the air. In other rare cases, people have been infected with pneumonic plague by their dogs or cats.

Risk factors

The risk of developing plague is very low. Worldwide, only a few thousand people develop plague each year. However, your plague risk can be increased depending on the area where you live and travel, your job, and your hobbies.


Plague outbreaks are most common in rural and semirural areas that are overcrowded, have poor sanitation and have a high rodent population. The greatest number of human plague infections occur in Africa, especially the African island of Madagascar. Plague has also been transmitted to humans in parts of Asia and South America.

In the United States, plague is rare, but it has been known to occur in several western and southwestern states — primarily New Mexico, Arizona, California and Colorado.


Veterinarians and their assistants have a higher risk of coming into contact with domestic cats and dogs that may have become infected with plague. People who work outdoors in areas where plague-infected animals are common are also at higher risk of getting plague.


Camping, hunting or hiking in areas where plague-infected animals reside can increase your risk of being bitten by an infected flea.

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Complications of plague may include:

Death. Most people who receive prompt antibiotic treatment survive bubonic plague. Untreated plague has a high fatality rate.

Gangrene. Blood clots in the tiny blood vessels of your fingers and toes can disrupt blood flow and cause that tissue to die. The portions of your fingers and toes that have died may need to be removed (amputated).

Meningitis. Rarely, plague may cause inflammation of the membranes surrounding your brain and spinal cord (meningitis).


You can take the following steps to prevent bubonic plague:

Make your home and yard inhospitable to rodents (mice, rats, squirrels) and other wild animals. Don’t leave places for them to hide or food for them to eat. This means cleaning up clutter, brush and other items and being careful when feeding animals.

Use flea control products for your pets, especially those who are allowed to roam freely. Take sick pets to the veterinarian immediately.

Don’t let pets who roam freely sleep in your bed.

Wear protective clothing — especially gloves — if you handle dead animals.

Use insect repellent if you go into wooded locations or other places that may expose you to fleas. Look for repellents that use DEET or permethrin.