Why the Bubonic Plague Is Not a Great Concern

Why the Bubonic Plague Is Not a Great Concern

China reported a case of the bubonic plague in a herdsman living in the northern city of Bayannur earlier this month. This morning, ABC News reported a squirrel testing positive for the disease in Colorado.

Hearing of recent cases of the bubonic plague naturally might make you feel uneasy as we continue to fight the COVID-19 Pandemic. After all, the disease did trigger the “Black Death” Pandemic in the mid-1300s. Black Death killed around 50 million in Europe alone. The pandemic continued for centuries, making it one of the deadliest diseases in history.


What is plague?

Plague is an infectious disease.  In 1894, Alexandre Yersin discovered Yersinia pestis, the bacterium responsible for plague, under a microscope. The most common carriers of Yersinia pestis are small mammals and their fleas. Fleas transmit the disease to mammals including humans. Therefore, transmission can take place from direct contact with a flea, or from an animal infected by the flea. There are three forms of plague: bubonic, pneumonic, and septicemic.


How does plague spread?

Many mammals are hosts of Yersinia pestis. These mammals include mice, rats, prairie dogs, rabbits, chipmunks, and squirrels. Rats are often associated with the plague. They were once a common catalyst for plague spread due to their close proximity to humans in crowded, unsanitary urban areas.

Recently, scientists discovered that Xenopsylla cheopis, a flea that lives on rats, is in fact the main cause of human cases of plague. After a rodent dies from plague, fleas jump to a new host, infecting the new host. Transmission also occurs through handling tissue or blood from a plague-infected animal, or inhalation of infected droplets.


What are the symptoms of plague?

Initial symptoms of the early stages of bubonic plague include vomiting, nausea, and fever. Bubonic plague’s name derives from buboes—swollen, painful lymph nodes which are also a symptom of plague. They occur around the armpit, neck, or groin.  These skin sores turn black, giving it its nickname “Black Death.”

Pneumonic plague is the most infectious type. This advanced stage of plague moves into the lungs. Pneumonic plague passes directly from person to person via airborne particles coughed from an infected person’s lungs.

Untreated, bubonic and pneumonic plague may progress to septicemic plague. Septicemic plague infects the bloodstream. Nearly all humans infected with pneumonic and septicemic plague die.


The beginning of plague in the United States

The first known cases of plague in the  United States occurred in 1900. Cases arrived in the U.S.  by rat-infested steamships, mainly those arriving from Asia. Epidemics in port cities were not uncommon.  In 1924-1925, the last U.S. urban plague epidemic occurred in Los Angeles. Plague then spread from urban rats to rural rodents, causing the disease to occur in more rural areas of the Western U.S.


Is plague common today?

Plague spread today is mostly sporadic. It pops up in countries all around the world each year including the United States. The World Health Organization reports 1,000 to 3,000 new cases of the disease every year. Plague is present on all continents with the exception of Oceania. Most human cases, however, have occurred in Africa since the 1990s. The top three countries that experience plague are Peru, Madagascar, and Democratic Republic of Congo (DRC) with DRC having the highest number of cases.

Scientists link the prevalence of plague in DRC to the mountainous terrain and tropical climate.  The most recent outbreak of plague happened in Madagascar in 2017 with more than 2,300 cases.

The United States, China, India, Vietnam, and Mongolia are common countries that report human plague cases. In the U.S., seven human cases of plague appear each year on average, emerging primarily in California and the southwestern states.


Is plague still deadly?

It is virtually impossible that the plague could become a pandemic due to modern medicine. Untreated, the plague still progresses to a deadly stage, but today, most people survive with rapid diagnosis and antibiotic treatment.  Antibiotics work best if given within 24 hours of symptoms. In severe cases, patients can receive oxygen, intravenous fluids, and breathing support. Those who have come into contact with an animal or person who has the plague may also take preventative antibiotics.


How do we prevent the spread of plague?

To prevent plague outbreaks, practice good sanitation, hygiene and pest control, and; minimize contact with wild animals that may carry infected fleas.



1 Yes the Bubonic Plague Is Still Around, Why You Don’t Need to Worry. Healthline. Ries, Julia. 7 July 2020.

2 Plague was one of history’s deadliest diseases—then we found a cure. National Geographic. Howard, Jenny.

3 PlagueWorld Health Organization.

4 Maps and Statistics, Plagues in the United States. Center for Disease Control and Prevention. 

5 Squirrel tests positive for the bubonic plague in Colorado. ABC News. Haworth, Jon. 14 July 2020.



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