top of page

Plague-Black Death


Plague is a contagious disease caused by the bacteria Yersinia pestis. This is a zoonotic bacteria, which means it can be spread from animals to humans. Plague is a very severe disease in people, particularly in its septicaemia (systemic infection caused by circulating bacteria in bloodstream) and pneumonic forms, with a case-fatality ratio of 30% to 100% if left untreated. In the past, plague caused widespread pandemics with high death rates. During the 1300s, it was called the "Black Death" because it killed more than 50 million people in Europe. Today, plague is easy to treat with antibiotics, and you can avoid getting it by taking normal precautions.

Plague is a Category A pathogen because it spreads easily from person to person and could kill a lot of people if not treated. This classification has added to fears that Y. pestis could be used as a biological weapon if it were spread as an aerosol. As a small particle in the air, it would cause pneumonic plague, which is the deadliest and most contagious type.

Stages of Plague

  • Bubonic plague, the disease's most common form, refers to telltale buboes—painfully swollen lymph nodes—that appear around the groin, armpit, or neck. The sores on the skin turn black, which is why it was called "Black Death" during pandemics. The first signs of this early stage are vomiting, feeling sick, and having a fever.

  • The most contagious kind of plague is called pneumonic plague. It is a late stage of plague that moves into the lungs. During this stage, the disease is spread directly from one person to another through coughed-up particles in the air.

If the bubonic and pneumonic forms of plague are not treated, they can turn into septicemic plague, which infects the bloodstream. Almost all people who get pneumonic or septicemic plague die if they don't get treatment.

Causes- Yersinia Pestis ( Bacteria)

  • For hundreds of years, no one knew what caused plagues, and superstitions grew around them. But careful observations and advancements in microscopes helped find out who was really to blame. In 1894, Alexandre Yersin found Yersinia pestis, the bacterium that causes the plague.

  • Y. pestis is a rod-shaped bacterium that is very dangerous. Y. pestis disables the immune system of its host by injecting toxins into defence cells, such as macrophages, that are tasked with detecting bacterial infections. When these cells are killed, the bacteria can grow without being stopped.

  • The bacteria live in the bodies of many small mammals, like rats, mice, chipmunks, prairie dogs, rabbits, and squirrels. During an enzootic cycle, Y. pestis can spread through populations of rodents at low rates, and most people don't know about it because it doesn't cause an outbreak. During an epizootic cycle, when the bacteria move from one species to another, people are more likely to get sick from them. People have thought for a long time that rats were the main cause of plagues because they live so close to people in cities. Scientists have only recently learned that the plague is mostly caused by Xenopsylla cheopis, a flea that lives on rats. When plague-infected rodents die, fleas move on to a new host, bite it, and spread Y. pestis. Handling tissue or blood from an animal with the plague or breathing in droplets that have the disease can also spread it.


  • A dramatic decrease in population was accompanied by significant economic and social changes in Europe. Wages rose as the labour force shrank, leaving ordinary people with a larger economic surplus.

  • The Black Death also increased religious persecution of Jews, who were blamed for spreading the disease. As Jews were blamed for the spread of the Black Death, anti-Semitism increased dramatically throughout Europe. A wave of violent pogroms followed, and entire Jewish communities were massacred or burned at the stake in large numbers.

Treatment and Prevention

  • Plague is a very serious illness that can be treated with antibiotics that are easy to find. The sooner a person with plague goes to the doctor and gets treatment for it, the better their chances are of making a full recovery.

  • Reduce the habitat for rodents around your home, workplace, and recreational areas. Remove any brush, rock piles, junk, cluttered firewood, and potential rodent food sources such as pet and wild animal food.

  • Wear gloves when handling or skinning potentially infected animals to avoid coming into contact with plague bacteria.

  • Apply flea control products to pets to keep them flea-free. Free-roaming animals are more likely to come into contact with plague-infected animals or fleas and bring them into homes.


bottom of page