Is COVID-19 a Plague?

California had its first case of plague in five years in August 2020 when a South Lake Tahoe resident was bitten by an infected flea. The news of the California case and other cases in China and Mongolia during the COVID-19 pandemic had people wondering whether there are similarities between COVID and the plague.

COVID is not the same as the plague, which is a bacterial infection caused by Yersinia pestis, but the infections share some similarities. Of note, people commonly use the word "plague" to describe any contagious disease that spreads rapidly, which could describe COVID. However, "the plague" refers to a specific bacterial infection.

Although plague is rare, the infection spread rapidly in the Middle Ages, similar to COVID in the 21st century. Plague and COVID both require isolation if you become infected. Learn more about the similarities and differences between COVID and plague symptoms, treatments, and more.

Plague Definition

Plague is a bacterial infection caused by Y. pestis, which caused widespread outbreaks in the Middle Ages. The infection is rare in the 21st century, thanks to antibiotics. An average of seven cases of plague have been recorded each year in the United States in recent decades.

Bubonic plague is a common type of plague that causes inflammation of the lymphatic system, which protects you from infections. Symptoms include:

• Aches
• Fever and chills
• Tender lymph nodes

Fever is also a common symptom of COVID, and some people report headaches. Other COVID symptoms include a dry cough, diarrhea, loss of taste and smell, and shortness of breath. Research has shown that about 40% of people with COVID do not develop symptoms.

Deadliest Plagues 

Three deadly plague pandemics have occurred throughout history. These pandemics include:

• Plague of Justinian: This pandemic began in 541 after Y. pestis emerged in Ethiopia and spread to Egypt. The bacteria spread to people through trading routes near the Mediterranean and later arrived in Constantinople, or modern-day Istanbul. As many as 100 million people died by 750.
• Black Death: The second plague pandemic occurred from 1347–1352. Y. pestis wiped out as many as 50% of Europe's population, which was more than 25 million people. People began to quarantine during this time, spending at least 30 days away from others.
• Third plague pandemic: Y. pestis emerged in Yunnan, China, in 1855 and spread through infected rats aboard ships on trade routes. The pandemic lasted until the mid-1900s and killed more than 15 million people.

COVID-19 and Plague Transmission

Plague is a bacterial infection that mostly spreads through the bites of infected fleas and rats. People can also become infected via direct contact with an infected animal, such as bites and scratches from cats. Although rare, person-to-person transmission may occur with pneumonic plague. This severe type of plague causes pneumonia, or inflammation of the lungs.

The virus SARS-COV-2 causes COVID, which is transmitted mostly from person to person. SAR-COV-2 spreads when an infected person breathes, coughs, sneezes, or talks within six feet of you. The virus less commonly spreads through the air and from infected surfaces.

Treatments

Antibiotics can readily treat plague. The risk of death increases if you are not treated within 24 hours of symptom onset. Some people may require intravenous (IV) fluids, oxygen, and respiratory support in a hospital. People with pneumonic plague must be isolated from others in a hospital. Close contacts will need to monitor their symptoms and take antibiotics as a precaution.

You'll similarly need to isolate from others if you test positive for COVID. The Centers for Disease Control and Prevention (CDC) urges people with COVID to isolate at home for five days from when their symptoms begin.

You can typically treat mild COVID symptoms at home. Antibiotics will not treat COVID, in contrast to plague. A healthcare provider can instead prescribe an antiviral, such as Paxlovid (nirmatrelvir with ritonavir), if you develop mild to moderate illness. People with severe illness might need treatment at a hospital.

Potential Complications

Y. pestis can quickly spread to other body parts if untreated. Plague can result in illnesses like meningitis and pharyngitis. Meningitis is inflammation of the membranes that cover the brain and spinal cord. Pharyngitis is inflammation of the oropharynx, or the middle of your throat.

The most severe complications arise from septicemic plague, which affects the blood, and pneumonic plague. These include septic shock and death.

Older adults and people with underlying health conditions are more susceptible to complications from COVID than others. Complications include:

• Acute respiratory distress syndrome (ARDS), which is a severe lung condition
• Acute respiratory failure
• Blood clots
• Pneumonia
• Septic shock

A Quick Review

COVID and plague share some similarities, but they are very different diseases. Plague is a bacterial infection, while COVID is a viral infection. The bites of infected fleas and rats spread plague. COVID, in contrast, is mostly spread from person to person. Both infections are treatable and require isolation from others while you recover.

The information in this story is accurate as of publication. However, as the situation surrounding COVID-19 continues to evolve, it's possible that some data have changed since publication. While Health is trying to keep our stories as up-to-date as possible, we also encourage readers to stay informed on news and recommendations for their own communities by using the CDC, WHO, and their local public health department as resources.