In the grim era before modern medicine, to quote a plaque located at London’s Old Operating Theatre museum, doctors’ coats were often “stiff and stinking with pus and blood.” One imagines a doctor would cut and bleed you, stitch you up, and then move briskly on to the next patient without time to preen at the washbasin between surgeries.

In Europe, protective doctor’s clothing first appeared in the form of a makeshift hazmat suit during the plague epidemics of the seventeenth century. Plagues, like famines, were a fact of life in the pre-modern world. Sometimes the plague came and went, carrying off only the weak and unfortunate; other times, as in the Great Plague of 1665, it felled the living like a farmer harvesting ripe wheat.

In the small town of Eyam in Derbyshire, England, a shipment of cloth bound for a local tailor sickened the tailor and his family. Guided by their clergyman, William Mompesson, the community chose to quarantine their small town of around seven hundred in hopes of stopping the plague’s spread. Elizabeth Hancock, a local farmer, watched as her husband and six children fell ill and, one after another, died. Hancock survived, but the plague had claimed 260 of the town’s inhabitants by November 1666.

In spite of the heroic sacrifice of the villagers of Eyam, the plague would not be stopped. With the onset of summer, in 1665, the fetid garbage and human waste of London made the city a rat’s paradise. As rats proliferated, so too did the sickness. In June, diarist Samuel Pepys wrote, “In the evening home to supper, and there to my great trouble hear that the plague is come to the City… but where should it begin but my good friend and neighbour’s, Dr. Burnett.” 

All in all, an estimated one hundred thousand people, a quarter of London’s population, died within eighteen months. Dr. Burnett, perhaps desperate to understand the plague and help treat those suffering, was one of a number of doctors who “attempted to open a dead corpse” that was covered in “tokens” of the plague, presumably gangrene or pustules. Likely working without gloves or masks, some doctors “fell down immediately, and others did not outlive the next day at noon.” 

Pepys, Dr. Burnett’s neighbour, never even fell ill. Dr. Burnett did not survive.

Yersinia Pestis, the plague bacteria, is a highly contagious, extremely unpleasant and very persistent little creature. While modern medicine has greatly diminished its impact, Y. pestis isn’t going quietly. In 2009, Malcolm Casadaban, a University of Chicago professor who was studying a weakened strain of the virus, suddenly fell ill and died. In 2014 and 2015, a total of twelve unlucky Coloradans—the plague thrives in open spaces replete with rodents—contracted it. Two died, including a sixteen-year-old named Taylor Gaes.  

Like rabies, it’s relatively rare to see contemporary human cases of the plague. When they happen—seven times a year or so in the United States—it’s usually in rural areas. Sometimes a hiker will become infected with Y. pestis after they take shelter in an animal burrow. Occasionally, a flea bite transmits the bacteria. Four of the non-fatal cases in Colorado in 2014 were linked to one dog. The dog’s owner contracted the disease, and when he brought his two-year-old pitbull to the vet, three veterinary clinic employees were exposed.

Once a human is infected, Y. pestis sets up shop in their body and gets to work. There are three different iterations of plague—pneumonic plague, septicaemic plague, and the infamous bubonic plague. Pneumonic plague occurs when the bacteria settles in the lungs. Coughing and fever occur, along with symptoms common to all three versions of the plague—headache, nausea and fever. In bubonic plague, the body’s lymphatic system becomes an unwilling host to Y. pestis, and alongside broad-spectrum symptoms, the lymph node closest to the point of infection swells up and becomes painful. Septicaemic plague is the most difficult to diagnose of the three. Gangrene and expulsion of blood from bodily orifices may or may not occur—you could just feel terribly unwell and slip into a coma before your results come back from the lab. 

The trouble is, the plague often feels just like the flu or pneumonia—until it doesn’t. If you contract Y. pestis, you’ve got between two and six days from the date of infection to seek medical attention. (Cross your fingers and hope you are correctly diagnosed.) What you want is antibiotics, and you want them fast. You might end up like Elizabeth Hancock, but even in 2017, it’s entirely possible you’ll end up like her husband and children.

When the bubonic plague struck France, Charles de Lorme was the king’s physician. The scion of a medical family that had attended to previous royal families, de Lorme was confident that miasma, or bad smells carried on the air, was the cause of the illness. He took steps to protect himself by creating one of the first full-body garments in Europe designed to ward off the “miasma”—essentially, an early biohazard suit. 

You’ve probably seen pictures of the plague doctor’s mask without ever knowing quite what it was. Perhaps you’re familiar with Swedish band The Knife, who wore similar masks while performing throughout the 2000s. Or maybe you know them as the curiously grotesque Medico della Peste masks, popular to this day at masquerades and carnivals in Europe.

The plague mask de Lorme developed completely covers the face. Glass lenses protect the eyes, and a long, curving, corvid beak protrudes over the mouth and nose area. The result is bizarre—de Lorme also wore a dark hood and shroud, and must have looked to his patients like a crow redolent of death. The long beak was made to be packed with scented herbs to prevent bad air from reaching the doctor. The glass lenses that filled the eye-holes were an attempt to keep spittle, pus, and blood out of the doctor’s eyes. The doctor wore heavy leather gloves, and even carried a stick to prod the patient, further removing his risk of contraction by keeping physical contact to a minimum. 

De Lorme survived the plague. In an era when no one really understood the causes of the contagion, when medical practitioners frequently wore amulets and charms to ward off the plague, de Lorme’s suit was something of a creepy miracle. 

In the pre-germ-theory era of medicine, when childbirth was the great killer of adult women, Doctor Ignaz Semmelweis noticed that women admitted to give birth in one division of the clinic at the Vienna General Hospital in the 1840s had a much higher mortality rate than women admitted to give birth in another. He noticed, more importantly, that women who literally gave birth in the street had a better survival rate than women who gave birth in the high-mortality division.

Since the two divisions used exactly the same techniques, Semmelweis began hunting for variables. He realized that while both divisions were part of the hospital’s teaching apparatus, the low-mortality division was staffed most often by midwives, and the high-mortality division most often by medical students—who might start their day with a dissection of last night’s unfortunates, before wiping their hands on a towel, or their black tailcoat and breeches, and heading up to see labouring and immediately post-partum women.

Semmelweis theorized that something too tiny to see with the naked eye, insidious and deadly, was being transmitted by the medical students. When he asked them to thoroughly wash their hands between seeing cadaver and patient, the mortality rate dropped 90 percent.

When Semmelweis published his findings in 1861, nothing immediately changed. Doctors at other hospitals reacted with scorn and derision. After all, Semmelweis was implying something dreadful: if washing a doctor’s hands resulted in fewer deaths, then it was the doctor who was making the patient sick.

Doctor reticence or not, times were changing. In 1854, physician John Snow had conclusively linked an outbreak of cholera to a contaminated public water pump. In 1858, The Great Stink of London drove parliament out of the city, and civil engineer Joseph Bazalgette successfully lobbied to construct a sewer system of the sort unseen since the Roman Empire: colossal, complex, an engineering marvel. Slowly, Europeans began to refigure cleanliness next to godliness. White clothing and linens, once rare, rose in popularity. Queen Victoria wore a white wedding gown, setting a trend; white lace curtains became a middle-class status symbol; hand-soap, which had been heavily taxed, hard to obtain and reserved only for the wealthy lady’s toilette, became a mass-produced, middle-class trend. 

In the world of medicine, one species of medical man had been wearing white for a while now—the lab technician. Doing work that tended to be less gruesome than a surgeon or a doctor on rounds, they had worn white or cream smocks since at least the 1820s. In the Victorian era, white came out of the lab and entered the consulting room. White lab smocks, white sheets, white doctors’ coats—patients could judge the piety and hygiene of their physician simply by looking at them. 

Medical practitioners will always be at greater risk of contracting—and passing on—illnesses than members of the public. Though doctors and nurses work hard to manage these risks, aided by disposable gloves, masks and gowns, nosocomial (or hospital-borne) transmission is still a factor in outbreaks of highly contagious illnesses like Ebola and SARS, as well as infections like methicillin-resistant Staphylococcus aureus (MRSA) and C. difficile. 

Though the white coat continues to be synonymous with modern medicine—“white coat ceremonies” are held for med school students, and the coat is presented as a sacred mantle—medical garb has continued to evolve. When obsessive whiteness caused a curious problem for doctors in surgery—the surrounding snowy field can cause colour fatigue in the surgeon, leading to the patient’s reds and pinks blurring together in a haze—medical guidelines changed, and we began to use blues and greens for surgical scrubs and draperies as well as nurses’ uniforms. 

Still, the white coat is a reminder to doctors that, despite powerful and impressive advancements in medical knowledge and theory, they are still on the front lines of transmissible diseases. The coat remains a symbol of their covenant with patients and a memorial for the fatal ignorance and negligence of the past.