Genes from extinct human cousins increase risk for severe COVID-19: Study

A group of genes passed down from extinct human cousins is linked with a higher risk for severe COVID-19, researchers say. 

Coronavirus patients with a snippet of Neanderthal DNA that crossed into the human genome some 60,000 years ago run a higher risk of severe complications from the disease, researchers have reported.

When they compared the genetic profiles of about 3,200 hospitalized COVID-19 patients and nearly 900,000 people from the general population, they found that a cluster of genes on chromosome 3 inherited from Neanderthals who lived more than 50,000 years ago is linked with 60 per cent higher odds of needing hospitalization.

People with COVID-19 who inherited this gene cluster are also more likely to need artificial breathing assistance, co-author Hugo Zeberg of the Max Planck Institute for Evolutionary Anthropology said in a news release.

The prevalence of these genes varies widely, according to a report published on Wednesday in Nature. In South Asia, roughly 30 per cent of people have them, compared to roughly one in six Europeans.

They are almost non-existent in Africa and East Asia. While the study cannot explain why these particular genes confer a higher risk, the authors conclude, "with respect to the current pandemic, it is clear that gene flow from Neanderthals has tragic consequences."

People infected with the new coronavirus, for example, who carry the genetic coding bequeathed by our early human cousins are three times more likely to need mechanical ventilation, according to the study.

There are many reasons why some people with Covid-19 wind up in intensive care and other have only light symptoms, or none at all.

Advanced age, being a man, and pre-existing medical problems can all increase the odds of a serious outcome.

But genetic factors can also play a role, as the new findings makes clear.

"It is striking that the genetic heritage from Neanderthals has such tragic consequences during the current pandemic," said co-author Svante Paabo, director of the department of genetics at the Max Planck Institute for Evolutionary Anthropology.

Unevenly distributed

They found that a Neanderthal individual from southern Europe carried an almost identical genetic segment, which spans some 50,000 so-called base pairs, the primary building blocks of DNA.

Tellingly, two Neanderthals found in southern Siberia, along with a specimen from another early human species that also wandered Eurasia, the Denisovans, did not carry the telltale snippet.

Modern humans and Neanderthals could have inherited the gene fragment from a common ancestor some half-million years ago, but it is far more likely to have entered the homo sapiens gene pool through more recent interbreeding, the researchers concluded.

The potentially dangerous string of Neanderthal DNA is not evenly distributed today across the globe, the study showed.

Some 16 percent of Europeans carry it, and about half the population across South Asia, with the highest proportion -- 63 percent -- found in Bangladesh.

This could help explain why individuals of Bangladeshi descent living in Britain are twice as likely to die from Covid-19 as the general population, the authors speculate.

In East Asia and Africa the gene variant is virtually absent.

About two percent of DNA in non-Africans across the globe originate with Neanderthals, earlier studies have shown.

Denisovan remnants are also widespread but more sporadic, comprising less than one percent of the DNA among Asians and Native Americans, and about five percent of aboriginal Australians and the people of Papua New Guinea.