The Plague: How a Medieval Killer Still Shapes Our Modern World
- gjohnston7
- Feb 24
- 5 min read
By Nishatur Ahmed
Edited by Glenn T. Johnston
The plague, often associated with the devastating Black Death that killed millions in Europe during the 1300s, is a serious bacterial illness that persists today, though it no longer poses the global threat it once did. Caused by the bacterium Yersinia pestis, it is primarily transmitted through fleas that bite infected rodents, particularly rats, and can spread rapidly in humans, becoming deadly if untreated. While a handful of cases still occur each year in rural areas of the western United States, the disease's history is intertwined with global trade, ships, ports, and human movement—reminding us that diseases require no passport to spread worldwide. This makes the plague relevant even to East Coast locations like the Port of Baltimore, where vigilance against imported threats has long been essential.
The plague affects the body aggressively once a person is infected. Victims typically experience fever and chills, severe fatigue, muscle aches, and painful, swollen lymph nodes. In its more severe forms, such as pneumonic plague, it can lead to organ failure, tissue death (which gave the Black Death its "black" appearance due to blackened extremities), and pneumonia that spreads person-to-person through respiratory droplets. Fortunately, modern antibiotics make the disease treatable when caught early, but without prompt treatment, it remains highly fatal. This underscores the critical importance of public health monitoring and swift response to any new cases.
The plague struck in three major pandemics: the Plague of Justinian (541 CE), the Black Death beginning in 1347, and a third pandemic originating in China in the late 19th century. Each spread through maritime trade networks, carried by infected rodents aboard ships linking port cities across the Mediterranean, Europe, Asia, and eventually the Americas. These outbreaks dramatically altered economies, decimated populations, and transformed approaches to health and sanitation—from early reliance on religious explanations and ineffective or harmful remedies (such as bloodletting or bathing in urine) to the scientific breakthrough in 1894 when the bacterium was identified as the cause, paving the way for effective prevention and treatment. Over time, responses evolved into modern public health practices focused on sanitation and medical intervention.
The most famous connection occurred during the Black Death, the second plague pandemic from 1347 to 1351, which killed an estimated 25 to 50 million people in Europe—up to 30–60% of the population in some regions. It originated in Central Asia and spread along trade routes, including the Silk Roads. It reached Europe via ships from the Black Sea region. In 1347, a fleet of about 12 ships arrived in Sicily, carrying plague-infected rats and fleas. From Sicily, the disease rapidly spread to other Mediterranean ports such as Genoa, Venice, and Pisa, then moved inland along trade networks and rivers.
Ports were especially vulnerable because ships transported goods such as grain and textiles that harbored rats and fleas, while crews and passengers could also carry the infection. Busy trading hubs connected distant regions quickly, turning them into both gateways for plague introduction and catalysts for its dissemination through global trade networks.
Venice pioneered quarantine in 1377, eventually requiring ships to isolate for forty days—quaranta giorni. It is from that phrase that the word “quarantine” originated. Permanent isolation stations known as lazarettos were built on islands to inspect crews, fumigate cargo, and monitor suspected cases. The system spread across Europe and later to American ports.
Baltimore has never recorded a single case of bubonic plague in its history, despite enduring other epidemics like yellow fever, typhus, and influenza. Nevertheless, the city stayed vigilant because the plague spreads so readily via ships, rats, and ports. In the late 1800s and early 1900s, global trade vessels frequently carried infected rats and fleas, posing a constant risk. While Western cities like San Francisco experienced outbreaks and the U.S. still sees around seven cases annually (mostly in rural Western states such as northern New Mexico, northern Arizona, southern Colorado, and parts of California, Oregon, and Nevada), Baltimore avoided infection through proactive measures. These included establishing quarantine stations to inspect arriving ships, fumigating vessels suspected of harboring rats, improving rat-proofing and sanitation at the port, and conducting rigorous public health inspections—even when such steps slowed trade. These efforts not only prevented disaster but also modernized the city's health systems, shipping practices, and sanitation standards.
In fact, the area directly across from Fort McHenry, where Rukert Terminal operates today, is called Lazaretto Point. There, the US Government established a quarantine station shortly after 1801. It was located at the junction of the city's southern and eastern boundary lines as they existed from 1816 to 1919. It is probable that the health officer boarded ships from the lazaretto until 1807, when his office was established in a large departmental building. Few detailed architectural drawings survive, but the site’s function as a quarantine station is well documented.
The plague came alarmingly close to the East Coast on occasion. In 1943, the French freighter Wyoming arrived in New York from Casablanca, Morocco, carrying rats despite a certificate claiming the ship was rat-free; testing confirmed the rodents were infected with plague, but prompt fumigation by public health workers contained the threat before it could spread. More recently, a 2015 Cornell University study revealed that New York City rats carried fleas capable of transmitting plague (though the fleas themselves were not infected), highlighting ongoing vulnerabilities. During the third pandemic, the disease reached 77 ports across five continents, including many in South America, and heavy U.S. trade with affected regions kept ports like Baltimore on high alert. This influenced quarantine laws, infrastructure improvements like cleaner sewers, and broader disease surveillance.
Even though human plague cases are now rare, its legacy endures in the foundations of modern public health, particularly in port cities. Global shipping still allows pests to hitch rides, and the surveillance systems and infrastructure developed during past plague scares continue to protect against future pandemics. The Port of Baltimore's ongoing commitment reflects how interconnected ports, trade, and global health truly are—one infested ship could threaten not just a city but an entire nation. The plague may feel like a relic of the past, but the public health systems that protect modern ports were built in response to it. The Port of Baltimore’s continued attention to inspection, sanitation, and surveillance reflects centuries of hard-earned lessons. In a world connected by ships and trade, vigilance remains the price of safety.
