Pneumonic Plague Mortality Rate


When people hear the world “plague”, most of them think of the plagues that Egypt experienced in the biblical times, which included swarms of locusts, hordes of frogs, and billions of lice. However, “plague” also refers to a certain disease that has killed people even in modern times.

Plague is caused by bacteria called Yersinia pestis, which reside in fleas and are usually transmitted by them. Yersinia pestis enter fleas when they bite mice, prairie dogs, and other rodents that are infected with these bacteria. Humans then acquire these microorganisms when get bitten by infected fleas or when they are exposed to other humans who are infected with the plague.

Forms of Plague

There are three forms of plague: bubonic, septicemic, and pneumonic. All of them are caused by the same bacteria; the only difference is the location of the infection in the body. The bubonic plague targets the lymphatic system, the septicemic plague infects the blood, and the pneumonic plague affects the respiratory system. Among these three, the pneumonic plague is the deadliest and the most difficult to control, although anyone can have bubonic, systemic, and pneumonic plague at the same time.

Mortality Rate of the Pneumonic Plague

In the early times, the pneumonic plague had a mortality rate of almost 100 percent. Unfortunately, this has barely improved even with the discovery of antibiotics and the development of strong and effective antibacterial medication. This comes from the fact that antibiotics must be administered within 24 hours of the first onset of symptoms, but not all infected people receive the appropriate treatment in time due to the lack of access to medical care. This is particularly true in developing countries, where many people live far away from hospitals and don’t always have the funds for healthcare.

If left untreated, the pneumonic plague has a mortality rate of 90 to 100 percent.

How the Pneumonic Plague Is Spread

Primary pneumonic plague is spread when an infected person coughs and releases bacteria into the air, and the microorganisms are breathed in by another person. It can also develop when a person handles the carcass of an infected animal. Secondary pneumonic plague happens when a person has already acquired the Yersinia pestis and the infection spreads to the lungs from the lymph nodes and/or the bloodstream.

Signs and Symptoms

The most obvious sign of the pneumonic plague is persistent coughing, which is often accompanied by hemoptysis, or the coughing up of blood. A person with the pneumonic plague will also develop fever, headaches, weakness, nausea, shortness of breath, and chest pain. There may be bloody or watery sputum.


When signs and symptoms of pneumonic plague are observed, the infected person must be rushed to the hospital ASAP so he can receive the appropriate treatment. As mentioned above, receiving antibiotics within 24 hours of the onset of symptoms can greatly reduce the possibility of death and increase the patient’s chances of survival. Those who have had close and direct contact with the patient, such as his friends and family members, should also receive antibiotic treatment to prevent them from acquiring the disease.