A plague on all our houses

PD Smith is gripped by Deadly Companions, Dorothy H Crawford’s fascinating study of man’s mortal combat with microbes.

From The Guardian:

DeadlycomYersinia pestis, the bacterium responsible for bubonic plague, is named after the Swiss microbiologist Alexander Yersin, who first identified it just over a hundred years ago. A relatively recent microbe in evolutionary terms, it spreads to humans via fleas that have gorged themselves on the infected blood of rats. Unless they have the universally fatal pneumonic version, plague victims themselves are not contagious. However, many people who experienced the Black Death in the 14th century were convinced it spread person-to-person. And strangely for a disease that also kills rats, not one eyewitness mentions seeing dead rats.

In a chapter of her fascinating study of the microbes that plague and sometimes aid us, microbiologist Dorothy Crawford asks whether the Eyam villagers really did die of bubonic plague. Records suggest that their disease was contagious. There is also the question of why isolation worked; after all, rats don’t obey quarantine. Some even doubt whether the black rats that carried the microbe could have survived in the cold climate of northern Europe. Indeed, rat fleas require a minimum temperature of 18C for their breeding cycles. Furthermore, the Black Death killed between 30% and 70% of the population, which far exceeds recent outbreaks that killed only 2%.

So which microbe did cause the Black Death, a disease that wiped out a third of England’s population in three years and killed 25 million people worldwide?

More here.