The Plague Never Went Away — And It Still Shows Up Every Year

Most people think of the plague as something from history books — a disease that wiped out millions of people in Europe hundreds of years ago. But the plague never actually disappeared. It still infects people today in parts of Africa and the United States, though it can now be treated with medicine called antibiotics.

Since the 1990s, most human cases of plague have been reported in Africa, especially in the countries of Congo and Madagascar. The World Health Organization, a global health agency, tracks these cases around the world. In the United States, about seven people get the plague each year on average, mostly in rural areas of the American West, according to the Centers for Disease Control and Prevention.

The plague recently made headlines when a worker at a plague research center in Siberia, a region of Russia, died of pneumonia. Some news reports suggested she may have died from a form of plague called pneumonic plague, though Russian officials said tests showed no signs of the disease. Still, the research institute was placed under quarantine, meaning people were not allowed to leave or enter the building.

Simon Clarke, a scientist at the University of Reading in the United Kingdom, said many people wrongly believe the plague is a thing of the past. "People think the plague is gone, it was something that occurred 500 years ago. It's not. It's here amongst us," he said. He added that as long as wild animals carry the bacteria, the disease will keep existing in nature.

The plague is actually very old. Scientists have found evidence that people in Siberia were dying from a form of plague at least 5,500 years ago. That early evidence came from the teeth of ancient hunter-gatherers who lived near Lake Baikal, a large lake in the region. This makes the plague one of the oldest known infectious diseases in human history.

There are three types of plague, and they are all caused by the same bacteria, called Yersinia pestis. The most well-known type is bubonic plague, also called the Black Death. It causes painfully swollen lumps called buboes, which appear in the groin, armpit, or neck. Other symptoms include sudden fever, chills, headaches, and pain in the stomach, legs, and arms.

The other two types are pneumonic plague, which infects the lungs, and septicemic plague, which is an infection in the bloodstream. Both can be deadly if not treated quickly. If bubonic plague is left untreated, it can turn into one of these more dangerous forms.

The plague usually spreads to people through flea bites. Fleas that have fed on infected animals like rats or prairie dogs can carry the bacteria and pass it to humans. People can also get plague by touching the body fluids of a sick or dead animal, so health experts say people should be careful when handling animals that may be ill.

Pneumonic plague can also spread through the air when an infected person coughs. However, Dr. Glenn Wortmann from MedStar Washington Hospital Center explained that the bacteria do not travel far. "You really need to be in face-to-face contact with that person to get pneumonic plague," he said. Because of this, he does not believe the disease will spread widely from Russia to other countries.

The good news is that the plague can be cured. When doctors catch it early and treat it with antibiotics, patients can fully recover. The key is to see a doctor quickly, because the disease can become very dangerous if it is not treated in time. There is a vaccine for the plague, but the World Health Organization only recommends it for people at high risk, like lab workers. No plague vaccine is currently available in the United States.