The plague, one of the most devastating bacterial infections in human history, caused the deaths of an estimated 50 million people in Europe during the middle Ages, where it was infamously known as the Black Death. While such large-scale outbreaks are a thing of the past, the plague still exists today, albeit in much smaller numbers.

In recent news, a man in New Mexico passed away from the plague in March after being hospitalized. Similarly, in February, a person in Oregon was diagnosed with bubonic plague, likely contracted from their pet cat. These cases, though rare, serve as a reminder that the plague is still around.

Transmission and Symptoms

The plague is primarily spread by fleas that live on rodents. When these fleas bite humans, they can transmit Yersinia pestis, the bacterium that causes the disease. The symptoms typically appear within one to seven days after infection and include fever, chills, coughing, and painful, swollen lymph nodes (called buboes) in the groin, armpit, or neck.

How Do Humans Get the Plague?

Humans can get the plague in several ways. The most common method is through the bite of an infected flea. People can also become infected by handling an animal that has the plague. According to the U.S. Centers for Disease Control and Prevention (CDC), cats, which can become sick from the plague themselves, can directly infect humans, while dogs, which are more resistant to the disease, might carry infected fleas back to their owners.

Moreover, the bacteria can persist in nature due to animal reservoirs. Certain rodents and their fleas maintain low levels of Yersinia pestis in the environment, making complete eradication challenging. This persistence is why occasional human cases still occur.

Geographic Occurrence

In the United States, the plague is mostly found in rural areas of the western states such as Arizona, California, Colorado, and New Mexico. On average, the CDC reports about seven human cases per year in these regions. Globally, however, the numbers are higher. Between 2010 and 2015, the World Health Organization (WHO) recorded 3,248 cases worldwide, resulting in 584 deaths. The Democratic Republic of the Congo, Madagascar, and Peru are the most affected countries.

Types of Plague

There are three main types of plague: bubonic, septicemic, and pneumonic. Bubonic plague, the most common form, affects the lymph nodes. If left untreated, it can progress to septicemic plague, which infects the bloodstream, or pneumonic plague, which affects the lungs and can be transmitted from person to person through respiratory droplets.

Historical Context and Modern Treatment

The massive death toll caused by the Black Death in the Middle Ages was primarily due to the absence of antibiotics, which were not discovered until centuries later. Today, modern antibiotics can effectively treat the plague if administered promptly. Streptomycin is typically the first-line treatment for both bubonic and pneumonic plague.

Dr. Dan Barouche, director of the Center for Virology and Vaccine Research at Beth Israel Deaconess Medical Center, explains that while the plague can be serious, it is usually treatable with antibiotics if caught early. Therefore, it should not induce the same level of fear that it did in the middle Ages.

Fatality Rates

According to the WHO, untreated bubonic plague has a fatality rate of 30% to 60%, while untreated pneumonic plague is almost always fatal. However, timely antibiotic treatment drastically reduces these risks. It is important to note that a strain of bubonic plague resistant to streptomycin has been identified in Madagascar, highlighting the need for continuous monitoring and research.

Vaccine Development

While there is a vaccine for Yersinia pestis, it is recommended only for people at high risk, such as scientists working directly with the bacterium. Dr. Harish Moorjani, an infectious disease specialist at Phelps Hospital in New York, notes that most people do not need the vaccine. Researchers are exploring various approaches to develop a more effective plague vaccine. Combining different types of vaccines may overcome the limitations of individual ones, potentially preventing future outbreaks.

Preventative Measures

To protect yourself and your family from the plague, it is crucial to eliminate potential nesting places for rodents around your home, such as brush, rock piles, trash, and excess firewood. If you encounter sick or dead animals, report them to law enforcement or health officials rather than handling them yourself. If handling is necessary, use gloves.

In areas where the plague is endemic, use insect repellents containing DEET to prevent flea bites and treat your pets for fleas regularly. Avoid sleeping with your pets, as this can increase your risk of contracting the disease. Additionally, prevent your pets from hunting or roaming in rodent habitats.