"The plague." The very name conjures up images of medieval towns where death stalks from door to door: a frightening, fatal disease from a dark period in history. But there are two important mistakes in this picture. First, plague still exists, though it only affects less than one person in a million worldwide each year. Second, plague is not always deadly, and it can be treated and cured.

What is the plague?

Plague is a rare but often life-threatening bacterial infection in humans. The bacterium Yersinia pestis causes three types of plague:

  • bubonic: The plague bacteria travel to the lymph nodes.
  • septicemic: The plague bacteria multiply in the bloodstream.
  • pneumonic: The plague bacteria multiply in the lungs and cause pneumonia.

General symptoms of plague include fever, weakness, and chills, all with a sudden onset. The three forms cause different symptoms in addition to this:

  • Septicemic plague causes pain in the abdomen and bleeding into major organs and the skin.
  • Bubonic plague causes swelling of lymph glands, called buboes. They may be tender to the touch.
  • Pneumonic plague rapidly causes pneumonia, causing shortness of breath, chest pain, and coughing. There may also be presence of bloody or watery mucus.

How does it spread?

Bubonic plague, the most common form, spreads by flea bites. Once an infected flea bites a person, the bacteria enter the host, causing infection. Infected fleas most often cause plague by biting small animals and rodents, including squirrels, rabbits, and prairie dogs, and a person can become infected if they are in close contact with these animals. The bacteria that cause the plague may also enter the body through a cut or wound.

Septicemic plague occurs when a person’s bloodstream becomes infected. Again, this typically occurs after an infected flea bites a human or animal. A person may also become infected after direct contact with infected materials through cracks in the skin.

Pneumonic plague is the least common form of plague. Primary pneumonic plague develops when a person breathes droplets containing the bacteria into their lungs. This type of pneumonic plague can be transmitted from person to person without involving fleas or animals. As a secondary infection, it develops after contracting another form of plague.

Who is at risk?

The risk of infection runs high for people who are in close contact with animals infected with plague bacteria or who spend time in flea-infested areas. Rats, squirrels, rabbits, and prairie dogs are common commonly infected with fleas that may pass on the infection. Breathing air that contains the bacteria is also a risk. Plague outbreaks can occur in rural areas and in cities that are overcrowded, have poor sanitation, and a high rodent population.

The bacterium that causes plague is found in a number of African countries, Asia, the former Soviet Union, and the United States.

How is it treated?

Treatment of plague relies heavily on strong antibiotics. With rapid diagnosis of symptoms and administration of antibiotics, treatment is typically effective. Anyone being treated for plague requires isolation from other patients in a hospital or other health care setting to minimize transmission to others.

Do plague outbreaks still occur?

Outbreaks of plague happen each year around the world, most with little or no media attention. Today's outbreaks do not compare to "The Black Death," a plague epidemic that killed approximately one third of Europe’s population during the Middle Ages. Today, annual deaths due to plague in humans hover between 1000 and 3000 worldwide.

Currently, no vaccine against plague exists. Plague is rare these days, largely due to better living conditions and sanitation and antibiotics. However, you can take precautions against contracting the infection.

What can you do to prevent infection?

Here are some tips:

  • Stay out of areas with large rat or rodent populations, as they may carry fleas that have the bacteria.
  • Wear proper clothing in areas with large flea or rodent populations.
  • Use flea-control products on your pets.
  • Avoid contact with people or animals that have the infection and seek immediate treatment if you are in contact with someone with plague, even if you do not have symptoms.

Gisèle Kane