There is only one disease with such a horrific history that its name is still used hundreds of years later to describe terrible illness. “He avoided her like the plague” is a common expression even though the disease itself is fortunately quite uncommon today. During the Middle Ages, plague was called the Black Death because of the flesh-blackening gangrene it caused in victims. In Europe, anywhere from 20 million to 30 million people died from the disease, and in some places the devastation was so severe there weren’t enough survivors to bury the dead.

What made the disease even more terrifying was that until around 1900, nobody knew what caused it or how to control it. Researchers were finally able to trace the disease to a bacterium that lives in rodent fleas. In the Middle Ages, homes and workplaces were typically infested with rats, which accounted for the fast spread of the disease.

Today, the World Health Organization reports 1,000 to 3,000 cases around the world every year. The United States rarely sees plague cases, but occasionally there are small outbreaks, usually in western states such as New Mexico, Arizona, Colorado, California, southern Oregon, and far western Nevada. In the United States, about 10 to 15 cases of plague are reported to the Centers for Disease Control and Prevention (CDC) each year. Veterinarians, cat owners, and people who hunt, camp, or hike in areas with plague-infected animals are more likely to come in contact with the disease.

Fortunately, today plague is treatable with antibiotics, and most people do recover.

How does plague spread?

The bacterium that causes plague still lives in the fleas that prey on rodents. But the bacterium-infected fleas can also feed on squirrels, rabbits, prairie dogs, and chipmunks. Your pet cat may even be a source of infection if it eats an infected rodent or is infested with plague-infected fleas.

Usually, the plague bacteria travel from rat to rat or squirrel to squirrel without spreading outside that specific animal population. But sometimes, when too many rats or squirrels die from the infection, the fleas invade other hosts, like wild rabbits and other animals. That’s when humans are more at risk. In 2008, a 50-year-old hunter in New Mexico caught a case of bubonic plague while skinning a wild rabbit. He was treated and recovered.

Plague appears in three forms:

Bubonic plague. This is the most common type of plague seen in humans. It is named for its characteristic swollen, infected lymph node, called a “bubo.” Usually only one lymph node is affected — most often in the groin. Other symptoms that may appear even before a bubo is noticeable (within two to eight days) include:

  • Sudden onset of fever and chills
  • Headache
  • Fatigue
  • Muscle aches

Septicemic plague. When bacteria in the infected lymph nodes spread to the blood, the result is septicemic plague. This type of plague can also be directly caused by a fleabite if the bacteria enter the bloodstream immediately. Symptoms of septicemic plague include:

  • Fever and chills
  • Abdominal pain, diarrhea, and vomiting
  • Bleeding from the mouth, nose, or rectum, or under the skin
  • Shock
  • Gangrene (tissue death and blackening) in the extremities, most often the fingers, toes, and nose

Pneumonic plague. This is the least common form of plague but the most deadly. It can develop when the bacteria from bubonic or septicemic plague spread to the lungs, or it can be transmitted directly by inhaling droplets from the cough of a person or animal infected with pneumonic plague. Symptoms usually appear within a couple of days of infection and include:

  • High fever
  • Weakness
  • Chest pain, difficulty breathing, and a cough that produces bloody sputum
  • Nausea and vomiting

What is the treatment for plague?

Anyone suspected of having plague should be immediately hospitalized and isolated to prevent the spread of the disease to others. Antibiotics are effective against plague, the most common ones being streptomycin or gentamicin. People who have been in contact with the patient should be checked for symptoms, and in some cases they will be given preventive antibiotics, too. These are usually administered intravenously in the hospital.

About one in seven people with plague will die from it. If it goes untreated, the mortality rate from bubonic plague can be as high as 60 percent. If septicemic or pneumonic plague isn’t treated, it is almost always fatal.

Can plague be prevented?

According to the CDC, plague will probably always exist in wild rodent populations, which serve as carriers for the infection; when there is a wider outbreak to humans, people can contract plague from each other. Public health officials try to contain its spread in three ways:

  • Controlling infected rodent populations
  • Educating people on ways to protect themselves
  • Administering preventive antibiotics to people who may have been exposed to the disease

Here are some ways to protect yourself if you live in one of the states where animal populations are known to be infected by the plague bacteria:

  • Remove brush, rock piles, rubbish and pet food from around your home to discourage rats.
  • Treat your dog or cat regularly for fleas. Ask a veterinarian for the best treatment for your animal.
  • Don’t touch dead animals. If you hunt, wear gloves when handling dead animals and use insecticide to kill fleas in the animal’s fur.
  • Keep an eye on your kids and pets when you are outside — especially in areas with large rodent populations. Use insect repellent on your skin and clothing.
  • When you go camping, resist the temptation to feed chipmunks and squirrels. They may look cute, but could infested with fleas that carry the plague bacterium.
  • Don’t camp, sleep, or rest near animal burrows.
  • When hiking, wear long pants tucked into boots to reduce your exposure to fleas.

Plague may continue to live on in the animal world, but a little diligence can keep it from becoming a problem for people.


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