It seems that the major epidemics suffered in the Middle Ages have been responsible for some Europeans being protected from AIDS. In fact, 10% of Europeans have some AIDS immunity, which is due to a mutation. Thanks to a mutation of the CCR5 protein in white blood cells, the virus that produces AIDS cannot enter white blood cells, so it cannot infect them.
Researchers don't know why so many people have that mutation in Europe. And in other places this mutation is very minority. One option might be that this mutation protected her from another disease and that is why it has spread. They have seen how the mutation occurred some 2,500 years ago, long before the onset of AIDS. And, in addition, it seems that it was in the Middle Ages when it became more common.
According to researchers from the British University of Liverpool, XIV. In the 18th century, between 1347-1350, the Black Death killed 40% of Europeans. So one in 20,000 people had a mutation. Subsequently, the plagues happened again and the last was the great London plague in 1660. At the same time, the frequency of the mutation increased considerably. Therefore, researchers believe that the mutation somehow protected the Black Death, so the plague contributed to the expansion of the mutation.
However, a group of London researchers disagree with them and believe that the key was baztanga. In fact, XVII. From the 20th century smallpox killed many people in Europe. In addition, the cause of smallpox, like AIDS, is a virus and that of the Black Plague, a bacterium, Yersinia pestis. They find it difficult for the same mutation to protect themselves before a bacterium and now from a virus.
However, those in Liverpool are able to explain why the mutation is more frequent in northern Europe. In Scandinavia and Russia, 16% of the population suffers mutation, while in Sardinia, for example, only 4%. According to the researchers, in Iparralde the plague XIX. It lasted until the nineteenth century, and therefore the mutation is more frequent than elsewhere.
It is really difficult to know who is right, but at least it is striking that the mutation that protected before an epidemic protects from the current one.