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Medically reviewed by Last updated on Apr 20, 2023.


Plague is a serious illness caused by a germ called Yersinia pestis. The germs mostly live in small rodents and their fleas. The most common way for humans to get plague is a flea bite.

Plague is a rare disease. The illness mostly occurs in only a few countries around the world. In the United States, plague affects a few people each year in rural or semirural areas of western states.

Plague usually can be treated with antibiotics. If not treated, the illness is often deadly.

Plague is considered a potential bioweapon. The U.S. government has plans and treatments in place if the disease is used as a weapon.


There are three types of plague. The symptoms vary for each type.

Bubonic plague

Bubonic plague causes swelling of lymph nodes. These are small, bean-shaped filters in the body's immune system. A swollen lymph node is called a bubo. The word "bubonic" is describing this feature of the disease.

If a person has bubonic plague, buboes appear in the armpits, groin or neck. Buboes are tender or painful. They vary in size from about less than half an inch (1 centimeter) to about 4 inches (10 centimeters).

Other symptoms of bubonic plague may include:

Septicemic plague

Septicemic plague occurs when plague bacteria multiply in the bloodstream. Buboes may not be present.

Early symptoms are very general and include:

More-serious symptoms may develop with advanced disease and organ failure. These include:

Pneumonic plague

Pneumonic plague affects the lungs. The disease may begin in the lungs, or it may spread from infected lymph nodes to the lungs. Symptoms can begin within a few hours after exposure and worsen rapidly.

Symptoms may include:

If treatment is not begun the first day, the disease progresses rapidly to failure of the lungs, shock and death.

When to see a doctor

Get immediate care if you have a sudden high fever.

Get emergency care if you have a sudden high fever or other symptoms and you live in an area that has had cases of plague. In the western United States, most cases have been in Arizona, California, Colorado and New Mexico.

Cases have occurred in Africa, Asia and Latin America. The countries with frequent cases include Madagascar, the Democratic Republic of Congo and Peru.


Plague is caused by a bacteria called Yersinia pestis. The bacteria circulate in populations of small animals and their fleas.

In the western United States, these animals include:

Other animals can get plague by eating small animals with the disease or picking up their fleas. These may include:

Disease in humans

People are most likely to get plague from a flea bite. The fleas are likely to come from small wild animals or from pets.

People also can get plague from direct contact with tissues of a sick animal. For example, a hunter can pick up the disease while skinning or handling an animal with the illness.

Pneumonic plague can be passed from animals to humans, or from humans to humans. Tiny droplets in the air can carry the bacteria when a person or animal coughs or sneezes. People can become infected when they inhale the droplets or touch coughed-up mucus.

Risk factors

The risk of getting plague is very low. Worldwide, only a few thousand people get plague each year. In the United States, seven people on average get plague each year.


Plague has been reported in nearly all parts of the world. The most common locations are Madagascar, the Democratic Republic of Congo and Peru. In Madagascar there is usually an outbreak of plague every year.

Plague has been reported in the western United States, most often in Arizona, California, Colorado and New Mexico.

The disease mostly survives in populations of rodents and their fleas in rural and semirural areas. It also has occurred in cities with overcrowding, poor sanitation or large rat populations.


People are at risk of getting plague if they work outdoors in areas where plague-carrying animals are common. People who work in animal clinics in these regions also have a risk of coming into contact with pet cats and dogs with the disease.


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


The U.S. government considers plague a possible biological weapon. Evidence exists of it being used or developed as a weapon in the past. The U.S. government has guidelines for treatment and prevention of plague used as a weapon.


Complications of plague may include:


The risk of death in people with all types of plague in the United States is around 11%.

Most people with bubonic plague survive with prompt diagnosis and treatment. Death is more likely with septicemic plague because it is difficult to diagnose and worsens rapidly. Treatment may unintentionally be delayed.

Pneumonic plague is severe and worsens rapidly. Risk of death is high if treatment doesn't begin within 24 hours after symptoms start.


No vaccine is available, but scientists are working to develop one. Antibiotics can help prevent infection if you were likely exposed to plague.

People with pneumonic plague are isolated during treatment to prevent the spread of disease. Health care workers must wear protective masks, gowns, gloves and eyewear when they treat someone with pneumonic plague.

Reducing the risk of exposure

If you live or spend time outdoors where plague occurs:


A health care provider will likely make a probable diagnosis of plague based on:

Treatment will likely start while your provider waits for the results of one or more laboratory tests to identify the Yersinia pestis bacteria. Samples for tests may come from:


Treatment for plague begins as soon as the health care provider suspects the disease. Treatment is typically done in the hospital. Antibiotics that may be used include the following:

Preparing for an appointment

Plague symptoms are sudden and serious. If you are coughing or sneezing, you should wear a mask.

You will likely go to an emergency room. If plague is suspected, you'll see a specialist in infectious disease.

What you can do

If you are helping a person with plague-like symptoms, you can prepare for the appointment by taking the following steps:

If plague is a possible diagnosis, you might ask the following questions or ask them on behalf of the sick person:

Don't hesitate to ask any other questions.

What to expect from your doctor

Your provider is likely to ask several questions, including:

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