The bubonic plague has emerged in Oregon for the first time in almost ten years.
Last week, health officials in the central region of Oregon reported that a person likely contracted the bubonic plague from their cat. Physicians promptly diagnosed the illness and administered antibiotics to the individual. Additionally, they traced and treated all contacts of the person and their cat as a precautionary measure. Consequently, authorities anticipate no further spread of the disease or fatalities.
The fundamentals of the plague are familiar to most individuals.
It is widely understood that during the 14th century, the plague resulted in the Black Death, a pandemic that potentially claimed 30% to 50% of the population in certain European regions, with an estimated death toll surpassing 50 million. Additionally, people are aware that the disease is transmitted through rodents and the fleas that bite them.
However, in the past decade, scientists have made significant advancements in understanding the plague and its effects on the human body. Here are several key revelations about the plague.
People of European Descent may Possess one (or two) Genes that offer Protection against the Plague
During the outbreak of the Black Death in Europe and the United Kingdom in the 1300s, it is believed that the disease not only reshaped society but also influenced the evolution of the human genome.
According to a study published in 2022, survivors of the plague in London and Denmark exhibited mutations in their genomes that conferred resistance to the plague-causing pathogen, Yersinia pestis.
Researchers identified four advantageous mutations in the genomes of these individuals. One of these mutations was estimated to increase the likelihood of surviving the plague by 40%, marking it as the most significant evolutionary advantage ever documented in humans for a single mutation, as per researchers interviewed by NPR.
These beneficial mutations were passed down to subsequent generations by survivors, resulting in many Europeans and Americans of European descent carrying these genetic variations today.
However, it is suggested that these advantageous genes may come with a trade-off. For instance, one of the mutations is associated with an increased susceptibility to autoimmune diseases like Crohn's disease.
Following years of Dormancy, the Plague has the Potential to Resurface in any Given Region
Annually, the world records between 200 to 700 cases of plague, although a significant number of cases likely remain undetected. The majority of these occurrences are concentrated in specific areas globally, with hot spots like Madagascar contributing to approximately three-quarters of reported cases. In the United States, fewer than a dozen cases are typically documented each year, primarily in the West.
However, the Yersinia pestis bacterium can manifest almost anywhere, including regions believed to have eradicated the disease or where it hasn't been observed for decades.
An instance of this resurgence occurred in Libya. After a 25-year absence of recorded plague cases, the disease reappeared in 2009. Initially, scientists speculated that the pathogen may have been introduced by an individual or animal from a neighboring country. However, analysis of the bacteria's DNA yielded a surprising revelation: the strain of plague in Libya closely resembled Y. pestis originating from Central Asia thousands of years ago, distinct from strains found in neighboring countries.
"We think the plague is extinct in these places, but it's not," microbiologist Elisabeth Carniel at the Institut Pasteur told NPR for a January 2013 story. "The plague is still there."
The whereabouts of the plague during periods of inactivity remain elusive, with speculation suggesting that it circulates undetected among rodents and the fleas they harbor. It's plausible that the bacterium exists at such low levels that it remains unnoticed for decades.
Even in the Presence of Antibiotics, one form of the Plague can Result in an Exceptionally High Fatality Rate
The plague presents itself in various forms depending on the body part invaded by the bacteria. When a person is bitten by a flea, they typically develop bubonic plague, characterized by swollen and painful lymph nodes known as buboes.
The term "bubonic" originates from the Greek word "boubon," meaning groin, as some individuals experience swollen lymph nodes in their groin area.
Diagnosis of the disease can be confirmed by extracting a sample from the person's blood or lymph nodes and submitting it to a laboratory for testing.
However, if the bacteria spread to the lungs, it can lead to pneumonic plague. Unlike bubonic plague, there are often no distinctive signs of the plague in this case, according to the Centers for Disease Control and Prevention.
Pneumonic plague poses a significantly greater risk, as explained by medical entomologist Adelaide Miarinjara from Emory University. "It transmits pretty easily between people because it spreads through droplets, almost like COVID spreads."
Moreover, people can die more quickly with pneumonic plague due to its swift progression. "The key here is early diagnosis. If people aren't expecting it or don't seek treatment, they can die."
In 2017, Madagascar experienced a large outbreak of pneumonic plague when an individual from a rural area introduced the disease to the coastal city of Toamasina. This city had not encountered a case of the plague in nearly a century, according to Miarinjara, who was present in Madagascar at the time.
The disease was transmitted via public transportation, resulting in over 2,400 suspected cases, including nearly 1,900 cases of pneumonic plague. A study estimated that approximately 25% of individuals with confirmed cases succumbed to the disease during this outbreak.
Plague Bacteria induce Vomiting in Fleas
In the western United States, various rodents, including chipmunks, squirrels, and prairie dogs, can harbor the plague bacteria, which they can transmit to humans through bites and scratches.
However, most of the time, rodents—and often humans—contract Y. pestis from a flea bite. Scientists now have a comprehensive understanding of how the flea transmits the bacteria during this process.
When a flea becomes infected, the plague bacteria reside within the insect's gut. Here, the bacteria produce a viscous, adhesive substance known as a biofilm. This film forms a small plug in the flea's throat, making it difficult for the insect to swallow. Consequently, when the flea bites an animal, it essentially regurgitates the biofilm—along with the plague bacteria—into the animal's bloodstream.
Microbiologist Viveka Vadyvaloo explained this process in a 2021 interview with the Washington State University Insider, stating, "You can imagine, you have something stuck in your throat and you try to take in some water but can't. You will vomit all that water out, and that's what happens to the flea. The blocked, starving flea will repeatedly bite its rodent or human host, creating more opportunities for infection."
The Black Death gave rise to the word "Quarantine"
The term "quarantine" originated from the Black Death pandemic, during which the city-state of Dubrovnik, now part of Croatia, implemented what is believed to be the first state-mandated isolation measure.
At that time, Dubrovnik, a prosperous merchant city situated along the Adriatic Sea, aimed to prevent the spread of bubonic plague. To achieve this, city authorities enforced a policy requiring visitors to spend 40 days on a remote island outside the city before being allowed ashore.
This waiting period was referred to as "quarantino," derived from the Italian word for "40."
According to Ivana Marinavić, head of educational programs at the Lazarettos of Dubrovnik, "the first quarantine was pretty much improvised." The Lazarettos, constructed specifically for quarantine purposes, were among the first buildings built for this purpose.
Breaking quarantine during the plague carried severe consequences. As Marinavić stated, "Torture, or cutting your nose or your ears off," were among the punishments imposed for non-compliance.
