What We Can Learn From the Black Death?

 The Black Death was far deadlier than COVID-19.  About 1/3 of Europe died in the 1348-51 outbreak.  Doubtless, many Europeans were not exposed.  But who survived and why?

First of all, the malnourished and others in poor health were disproportionately struck down.  1/28/08 Reuters:

An analysis of 490 skeletons from a London cemetery for Black Death victims demonstrated that the infection did not affect everyone equally, two U.S. scientists said on Monday.

While many perfectly healthy people certainly were cut down, those already in poor health prior to the arrival of the plague were more likely to have perished, they found.

“A lot of people have assumed that the Black Death killed indiscriminately, just because it had such massive mortality,” anthropologist Sharon DeWitte of the University at Albany in New York, said in a telephone interview.

People already in poor health often are more vulnerable in epidemics. “But there’s been a tradition of thinking that the Black Death was this unique case where no one was safe and if you were exposed to the disease that was it. You had three to five days, and then you were dead,” DeWitte said.

Think of these as comorbidities.  Some historians tie the malnutrition to the Little Ice Age.  12/10/20 Nature:

Cooler climate conditions during the Little Ice Age further weakened afflicted groups, making European populations less resistant to pathogens, through malnutrition and deteriorating living/sanitary conditions.

Today, the big risk factors include obesity, which is not not malnutrion but misnutrition.  3/8/21 CDC:

Overweight and obesity were risk factors for invasive mechanical ventilation. Obesity was a risk factor for hospitalization and death, particularly among adults aged <65 years.

Other risk factors.  5/13/21 CDC:

Main Findings:

• 29.9% of inpatients and 74.9% of outpatients diagnosed with COVID-19 had no comorbidities as defined in the study.
• The most common comorbidities were hypertension (30,236 [46.7%]), hyperlipidemia (18,744 [28.9%]), diabetes (18,091 [27.9%]), and chronic pulmonary disease (10,434 [16.1%]).

So what happened during the first big round of bubonic plague?  The comorbids died in large numbers.  Many people either came through with an acquired immunity or were lucky enough to be genetically superior.

Some scientist argue that people with the CCR-delta32 gene were if not immune to bubonic plague, at less at risk than the general population.  See 5/29/14 PBS:

Knowing who died and who lived through the early years of the plague is somewhat problematic. Deaths among the general English population were not recorded in the 14th Century — the height of the Plague — and most communities did not begin recording parish registers until around 1538. Fortunately, Eyam began keeping a parish register in 1630. Thus historian John Clifford began by examining the register, noting everyone who was alive in 1665, the year the plague came to Eyam. He searched for evidence of life through the year 1725 — marriages, baptisms, burials that took place years after the plague had left the village. Deleting the names of those lost during the plague period, he was able to determine who the survivors were....

After three weeks of testing at University College in London, delta 32 had been found in 14% of the samples. This is a genetically significant percentage, yet what, really, did it mean? Could the villagers have inherited delta 32 from elsewhere, residents who had moved to the community in the 350 years since the plague? Was this really a higher percentage than anywhere else? To find out, O’Brien assembled an international team of scientists to test for the presence of delta 32 around the world. “Native Africans did not have delta 32 at all,” O’Brien says, “and when we looked at East Asians and Indians, they were also flat zero.” In fact, the levels of delta 32 found in Eyam were only matched in regions of Europe that had been affected by the plague and in America, which was, for the most part, settled by European plague survivors and their descendants.

Those who are getting sick with COVID-19 are going to either die or recover.  Of those who recovered, 23.2% reported long-lasting symptoms.  Bubonic plague returned, killing fewer people each time.  2008 NIH:

Despite repeated claims in textbooks, the plague of Marseilles in 1720–1 was not this pandemic's European finale.4 In 1743, 48,000 perished from plague in Messina; in 1770–1 over 100,000 in Moscow; and in the Balkans, Egypt, Asia Minor and Russia this Black-Death-type of contagious plague may have persisted as late as 1879.5

The “third pandemic” began in the mid-nineteenth century and crept slowly through the Yunnan peninsula until it reached Hong Kong in 1894. From there, steamship commerce carried it across much of the world. However, except for China and India and a few other subtropical regions, its spread (unlike that of the other two pandemics) was limited in epidemic force to coastal cities and even there hardly penetrated beyond docklands. Instead of millions killed, as happened with the previous two pandemics and as Europe feared at the beginning of the twentieth century, death counts of this third pandemic in temperate zones rarely exceeded one hundred.

The Black Death killed off lots of peasants, many of them doubtless malnourished.  This improved peasants improved the economic bargaining power of those who survived.  (See Bertha Haven Putnam's The Enforcement of the Statute of Laborers (1908) if you want a very detailed examination.)   I would expect this improved their nutrition even as the Little Ice Age persisted.  Some of the drop was likely the increased CCR5-delta32 genes in the European population.  I suspect that we are going to find that those who survive this pandemic will include at least a few who carry similar genetic advantages against COVID-19.  The deaths of those with comorbidities will reduce mortality rates during the next pass of the Angel of Wuhan Death.

If you have a comorbidity over which you have any control (such as obesity) start working on it now.  I have managed with considerable effort (where's my cinnamon roll?) to go from obese to overweight.