A pandemic can have consequences centuries after it ends. This is the conclusion reached by the scientists who are the authors of a study published in the scientific journal Nature this Wednesday.
The study authors wanted to see what genetic conditions favored survival from the Black Death. The Black Death, which swept through Europe, West Asia, and North Africa in the mid-14th century, was an infectious disease that killed up to 50% of Europe’s population. Scientists have analyzed the DNA of more than 200 people who died in London and Denmark shortly before, during and shortly after the epidemic.
In London, DNA was taken from three cemeteries close to each other, closely dated using archaeological techniques and historical records. In Denmark, the DNAs came from people buried in five locations, spread across the country, and were dated by means similar to those in London.
Genes that promote pest survival
The results showed that four genes were associated with survival from the Black Death. A gene is a piece of DNA that contains the information needed to make a protein.
“The high mortality rate” of the Black Death suggests that the genetic variants that conferred protection against infection “may have been subject to strong selection during this period,” the study continues.
“Indeed, the nearly decade-long plague epidemics in the four hundred years after the second pandemic in Europe have often (but not always) been associated with reduced mortality rates,” which may be related to human genetic adaptation , the authors write.
A gene that has spread through the population.
People with the ERAP2 gene in particular, being less affected by the plague, passed this gene on to their children, developing greater resistance to this disease in the population. The study estimates that people with this gene in the Middle Ages had a 40% better chance of survival than those without it.
It was present in 40% of people who died before the Black Death in London, compared to 50% afterwards. In Denmark, this change is even more markedfrom 45% to 70%.
Thus, “the Black Death shaped the evolution of immune genes,” Luis Bruno Barreiro, geneticist and co-author of the study, explains on Twitter.
This selection, however, had other consequences, which affect the health of some people even today. The ERAP2 gene, which stimulates a particularly effective immune response against plague and was therefore subsequently transmitted, is also “associated with increased susceptibility to autoimmune diseases”, according to the study.
Possessing the ERAP2 gene is, for example, a risk factor for Crohn’s disease, a chronic inflammatory bowel disease that affects nearly one in 1,000 people in France, according to health insurance. The study’s authors believe the latter demonstrates “the role that past pandemics played in determining current vulnerability to disease.”
Source: BFM TV
