Individuals who suffer a severe COVID-19 infection may perhaps blame genes inherited from our cousins the Neanderthals. A new study focused on the northern Italian city of Bergamo, an early epicenter found to have one of the world's highest COVID-19 death rates, links a set of DNA variants, or a haplotype, inherited from Neanderthals to the development of severe respiratory illness. In a sample of nearly 10,000 residents of the Bergamo area, those with the haplotype were twice as likely to develop severe pneumonia from COVID and three times as likely to be hospitalized in intensive-care units and placed on ventilators as those without the haplotype, reports the Wall Street Journal.
People of European and Asian origin inherited about 2% of their genomes from Neanderthals through their interbreeding with modern humans. A 2020 study that first linked a genomic segment inherited from Neanderthals to severe COVID found about 16% of Europeans and 50% of South Asians carry it. About 33% of Bergamo residents who developed life-threatening forms of COVID had the Neanderthal haplotype, which was less present in people who developed mild COVID symptoms or no symptoms at all, says Giuseppe Remuzzi, director of Milan's Mario Negri Institute for Pharmacological Research and lead author of the study published last month in iScience. The study notes this particular haplotype is "the major genetic risk factor for severe COVID-19."
Neanderthal genes have been tied to increased susceptibility to a variety of diseases affecting modern humans, from alcoholism to obesity, per IFL Science. Another study published in March linked Neanderthal genes to an increased risk of immune dysregulation disorders in response to COVID, per Insider. Still, genetics doesn't fully explain why Bergamo was so hard hit by the coronavirus. For one thing, it's not known what percentage of residents carry the haplotype. The study does point to a possible explanation for less severe forms of COVID in Africa, though. As the Journal notes, the Neanderthal haplotype is "almost completely absent" from the continent, which has the youngest population of any other. Italy, in comparison, "has one of the oldest populations in the world." (Read more COVID-19 stories.)