Human Plague: What It Is, What Causes It and How to Prevent It

Two confirmed cases of the human plague in New Mexico in June 2017 brought the flea-borne infectious disease, the human plague, into the limelight. The word “plague” instills concern just by its mention, but the good news about this human plague is that it is treatable with antibiotics.

History of the Human Plague

The “Black Death” or Great Plague that originated in China then spread along trade routes to Europe and areas in between is likely the most widely known of the plague pandemics. (Pandemic being a large epidemic – something that covers a region, country, etc.) Another term used for this plague pandemic was Bubonic Plague, so named due to the swelling of lymph nodes in many people with the infection, one of the three types of human plague.

The Great Plague, having taken place in the 14th century when it was responsible for the deaths of 60 percent of the European population,  was the second of the major plague pandemics. The first recorded plague pandemic occurred in the 6th century in the Mediterranean region of the world with outbreaks ongoing for more than 200 years, resulting in the deaths of 25 million people.

The third plague pandemic, occurring in the 19th century also originated in China and resulted in the deaths of about 10 million people. It was during this pandemic that scientists were able to identify the causative organism of the plague, that of the bacterium Yersinia pestis, spread by the bite of infected fleas and contact with infected small rodents, from rats to squirrels, prairie dogs and others.

What Is the Human Plague?

The human plague is a highly contagious but curable infectious diseases caused by the Yersinia pestis bacterium carried through flea bites of fleas who have bitten infected animals and carry the bactierium within them, only to spread it to other animals – and humans – that they bite.

In addition to bites from infected fleas, humans can be exposed to the causative bacterium through a break in the skin by handling infected animals or infected animal carcasses.

The most rare form of human plague, that of pneumonic plague, is spread by breathing droplets in the air from infected animals or other humans.

Domestic animals such as dogs and cats can also be infected by the Yersinia pestis bacterium either through the bites of infected fleas or contact with infected animals.

There are a number of positive facts about the human plague in the 21st century:

  • On average, human plague affects 5,000 or fewer people throughout the world each year
  • The human plague is curable with the use of antibiotics with prompt treatment
  • The highly contagious form of human plague is also its rarest form, where the infection is present in the lungs, allowing an easy transmission between humans.

There are three main types of human plague, named for the body systems involved in the infection:

  • Bubonic – the most common form of the human plague, this infection involves the lymph nodes.
  • Septicemic – an infection in the bloodstream
  • Pneumonic – an infection in the lungs

What Are the Symptoms of Human Plague?

There are generalized symptoms that may be associated with all three types of the human plague and some symptoms that are specific to the type of infection present.

Generalized Symptoms of Human Plague

Sudden onset of:

  • Fever
  • Chills
  • Headache
  • Weakness

Type-Specific Symptoms of Human Plague


  • Swollen lymph nodes within a week of generalized symptoms – may affect neck, armpits and/or groin
  • The swelling may become about the size of a chicken egg and be warm and tender to the touch
  • Extreme weakness
  • Abdominal pain, diarrhea, vomiting
  • Bleeding from the mouth, nose or rectum or under the skin
  • Shock
  • Blackening and gangrene of tissues in extremities, most often fingers, nose and/or toes


Symptoms progress quickly in this, the rarest form of human plague. Treatment with antibiotics must begin within the first day of symptoms to prevent the infection from becoming fatal. The generalized symptoms, in addition to these symptoms below, begin within hours of becoming infected. 

  • Cough with bloody sputum
  • Difficulty breathing
  • Nausea and vomiting
  • If left untreated, pneumonic human plague can progress to respiratory failure and shock within two days of the initial infection.

Where Does Human Plague Occur?

Human plague can occur anywhere in the world, but in current times, it has occurred most often in parts of Africa, with some areas of the U.S. Southwest (Arizona, California, Colorado and New Mexico) averaging five to fifteen cases each year.

How Can You Prevent Becoming Infected with Human Plague?

Many of the preventive measures to protect human against becoming infected with the plague also protect pets from the infection:

  • Use appropriate flea control measures for your pets and home
  • Keep pets at home or on a leash at all times
  • Keep areas around your home and yard free of debris and clutter to reduce the amount of places rodents can hide or nest
  • Take a sick pet to the veterinarian for diagnosis and treatment. An infected pet may not only die from the plague, but also infect any fleas that may bite it, exposing more animals and humans to infection.

Caveat: This article is informational only in nature and not intended to be used as a substitute for medical advice from a health care professional.

Share with your friends

Follow Us

Enter your email address to get updated when we have new posts on the site and never miss a thing:

Delivered by FeedBurner

Leave a Reply

Your email address will not be published. Required fields are marked *