The Calculus Diaries - Jennifer Ouellette [61]
The plague spread rapidly and was so virulently infectious that even doctors feared treating victims. At the time, they believed the disease spread via “bad air,” or miasmas. Those who did treat patients took what precautions they could, donning large beaked hats made of bronze and stuffing the “beak” with strong herbs and spices to purify the air the doctor breathed. (As an added bonus, the aroma from the herbs helped mask the stench of rot that invariably accompanied the plague.) Plague doctors dressed in pants and a long gown and wore leather gloves, as well as crystal eyepieces for added protection— anything to ward off contamination, even though the source of the plague was not identified until the nineteenth century. All clothing, even undergarments, were doused in camphor oil or treated with wax to further seal the doctor from bad air.
These precautions might have been partially effective. We now know that plague is caused by a bacillus called Yersinia pestis and is spread by rodents and their fleas to humans.35 Protecting the eyes, nose, and mouth made it harder for Y. pestis to get into the body via mucous membranes, and coating one’s clothing with wax made it more difficult for fleas to penetrate to the skin and transmit the disease with their bites. And the herbs stuffed into the beak of the mask at least partially blocked breathing holes, so the doctor would be less likely to inhale the bacillus. Their Achilles’ heel was actually the ankles, which remained exposed and therefore vulnerable to flea bites.
The credit for this momentous discovery goes to a French scientist named Alexandre Yersin, a former student of Louis Pasteur.36 Yersin went to Hong Kong in 1894 to investigate an outbreak of the plague there. He extracted some of the pus from a dead soldier’s bubo (swollen lymph node) and injected it into guinea pigs; all the guinea pigs died. He examined the pus from both the dead soldier and the doomed rodents and noticed both samples contained the same type of bacteria. Yersin also noted the large number of dead rats around the city, examined those bodies, and once again observed the same bacteria. Conclusion: Y. pestis was the culprit for the spread of plague.
Yersin did not determine the means of transmission, however. That honor fell to his fellow scientist, Paul-Louis Simond, who experimented with infected rats and fleas. He noticed that even if he placed an infected rat into a jar with healthy rats, the healthy ones only became sick if fleas were present. Just how virulent is this plague-causing Y. pestis? In lab experiments, mice died after being infected with just 3 bacilli; your average flea can transmit 24,000 in a single bite.
Plague has many different vectors: It can spread person to person or via the rats and fleas; which type you get depends on how the bacillus invades your body. The Black Death came in three forms: bubonic, pneumonic, and septicemic. After the bite of an infected flea, the first site of infection is generally the lymph nodes. In this form, bubonic plague, your lymph nodes swell to form enormous buboes. Lancing the buboes releases oozing, foul-smelling pus. The bubonic plague was the most common form, with a mortality rate of 30 to 75 percent. In addition to enlarged and inflamed lymph nodes around the armpits, neck, and groin, victims were subject to headaches, nausea, aching joints, high fever, and vomiting, and symptoms took from one to seven days to appear.
The pneumonic plague, infecting the lungs, is particularly virulent, capable of killing an infected person within twenty-four hours. You would catch this merely by breathing Y. pestis into your lungs. The mortality rate for the pneumonic