THE PATHOGEN
Yersinia pestis
A rod-shaped bacterium carried by fleas living on rats and other rodents. One bite from an infected flea can pass it on. It causes bubonic plague (swollen, painful lymph nodes called buboes), septicemic plague in the blood, and pneumonic plague in the lungs, the only form that spreads person to person through the air. Today it is treatable with antibiotics, and a few thousand cases still occur worldwide each year.
1347–1351
The Black Death
Arriving in Europe on trading ships through Black Sea and Mediterranean ports, plague swept the continent in about four years, killing an estimated 25–50 million people, between a third and half of Europe's population. Whole villages emptied. The word "quarantine" comes from the Venetian quaranta giorni: the 40 days ships had to wait offshore before landing.
THE ICON
The Plague Doctor
The beaked mask is mostly a 17th-century image, credited to Charles de Lorme, physician to French kings. The beak was stuffed with herbs, spices and perfume, since people believed disease spread through foul air, or "miasma". A waxed leather coat, gloves, a wide hat and a wooden cane let the doctor examine patients without touching them. Many were hired by towns to treat everyone, rich or poor.
THE LEGACY
Why It Still Matters
Plague reshaped history: labor shortages raised wages and weakened feudalism, cities invented public health boards, and the outbreaks pushed medicine toward observation and science. In 1894 Alexandre Yersin identified the bacterium in Hong Kong, which is why it carries his name. The plague doctor became a lasting symbol of watching, warning and surviving, which is what this tracker is built around.