The plague is a serious bacterial infection that can be deadly. Sometimes referred to as the "black plague," the disease is caused by bacteria called Yersinia pestis. This bacteria is found on animals throughout the world and is usually transmitted to humans through fleas.
The risk of plague is highest in areas that have poor sanitation, overcrowding, and a large population of rodents.
In medieval times, the plague, or "black death," was responsible for the deaths of millions of people in Europe. Today, there are only 1,000 to 3,000 cases reported worldwide each year, with the highest incidence in Africa.
Plague is a rapidly progressing disease that can lead to death. Immediate medical intervention is necessary.
There are three basic forms of plague.
The most common form of plague is bubonic plague. It is usually contracted when an infected rodent or flea bites you. In very rare cases, you can get the bacteria from material that has come into contact with an infected person.
Bubonic plague infects your lymphatic system (immune system), causing inflammation. Untreated, it can move into the blood and cause septicemic plague, or to the lungs, causing pneumonic plague.
When the bacteria multiply in the lungs, you have pneumonic plague—the most serious form of the disease. When a person with pneumonic plague coughs, the bacteria from their lungs are expelled into the air. Other people who breathe that air can also develop this highly contagious form of plague, which can lead to an epidemic.
When the bacteriamultiply in the bloodstream, it is calledsepticemic plague. When untreated, both bubonic and pneumonic plague can lead to septicemic plague.
People usually get plague through the bite of fleas that have previously fed on infected animals like mice, rats, rabbits, squirrels, chipmunks, and prairie dogs. It can also be spread through direct contact with an infected person or animal, or by eating an infected animal. According to the National Institutes of health, plague can also spread through scratches or bites of infected domestic cats (NIH).
It is rare for bubonic plague or septicemic plague to spread from one human to another.
Bubonic Plague Symptoms
Symptoms of bubonic plague generally appear within two to seven days and 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 gives bubonic plague its name.
Pneumonic Plague Symptoms
Pneumonic plague symptoms may appear as quickly as one day after exposure to the bacteria and include:
- trouble breathing
- chest pain
- overall weakness
- bloody sputum (saliva and mucus or pus from the lungs)
Septicemic Plague Symptoms
Septicemic plague symptoms usually start within two to seven 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
- bleeding (blood may not be able to clot)
Plague is a life-threatening disease. If you have been exposed to rodents or fleas, or if you have visited a region where plague is known to occur, contact your doctor immediately if you develop symptoms of plague.
Be prepared to advise your doctor of recent travel locations and dates. Tell your doctor about all your symptoms and when they first appeared.
Make a list of all over-the-counter medications, supplements, and prescription drugs you take. Make a list of people who have had close contact with you.
When you visit the doctor, emergency room, or anywhere else where others are present, wear a surgical mask to prevent spreading the disease.
If your doctor suspects you may have plague, he or she will look for the presence of the bacteria in your body.
A blood test can reveal if you have septicemic plague. To check for bubonic plague, your doctor will use a needle to take a sample of the fluid in your swollen lymph nodes. To check for pneumonic plague, fluid will be extracted from your airways by a tube that is inserted down your nose or mouth and down your throat. This is called an endoscopy.
The samples will be sent to a laboratory for analysis.
The plague is a life-threatening condition that requires urgent care. If you have symptoms of plague, your doctor may start you on antibiotics before laboratory results are in.
With no treatment, bubonic plague can multiply in the bloodstream, causing septicemic plague, or in the lungs, causing pneumonic plague. Death can occur within 24 hours after the appearance of the first symptom.
Treatment usually involves powerful antibiotics, intravenous fluids, oxygen, and sometimes breathing support. People with pneumonic plague must be isolated from other patients. Medical personnel and caregivers must take strict precautions to avoid getting or spreading plague.
Anyone who has come into contact with pneumonic plague patients should also be monitored and are usually given antibiotics as a preventative measure.
Without medical intervention, about 50 percent of people who have bubonic plague and almost 100 percent of people with pneumonic plague die, but treatment reduces the death rate to 50 percent for both varieties (NIH).
Plague can lead to gangrene if blood vessels in your fingers and toes disrupt blood flow and cause death to tissue. In rare cases, plague can cause meningitis, an inflammation of membranes that surround your spinal cord and brain.
Keeping the rodent population under control can greatly reduce your risk of getting the bacteria that causes plague.
Keep your home free from stacks of firewood or piles of rock, brush, or other debris. Don’t leave pet food out and protect your pets from fleas. Use insect repellent products or natural insect repellants like citronella when spending time outdoors.
If you have been exposed to fleas during a plague outbreak, visit your doctor immediately so your concerns can be addressed quickly.
A vaccine is available, but is only recommended as a preventative measure for high-risk groups (like laboratory staff). According to the World Health Organization, the vaccination is not a proven method of preventing plague during an outbreak (WHO).
Epidemics of plague killed millions of people (about one-third of the population) in Europe during the Middle Ages. It came to be known as the "black death."
Today the risk of developing plague is quite low, with only 1,000 to 3,000 cases reported worldwide each year (WHO). Outbreaks are generally associated with infested rats and fleas in the home. Crowded living conditions and bad sanitation also increase the risk of plague.
The disease is still found in Asia, Africa, and South America. The highest incidence of infection in humans occurs in Africa. However, the largest number of infected animals is in the United States—mostly in Arizona, Colorado, and New Mexico. The former Soviet Union also has a large population of infected animals.
The last epidemic of plague in the United States occurred in 1924-25, in Los Angeles. It is rare today, with only about 10 to 25 cases reported each year (CDC).