University of Oxford scientists have uncovered a gene that doubles the risk of lung failure and death from Covid.
They say 60% of people from South Asian backgrounds and 15% of people of European ancestry carry the high-risk version of the gene.
The Nature Genetics study sheds light on why some communities in the UK and South Asia are at higher risk from Covid - but does not fully explain it.
Building on previous genetic work, researchers used a combination of artificial intelligence and new molecular technology to pinpoint the exact gene - called LZTFL1 - responsible for the increased risks.
They estimate the risky version of the gene is present in about 2% of people from African-Caribbean backgrounds and 1.8% of people of East Asian decent.
Lead researcher Prof James Davies said the discovery that the risky gene does not affect all populations equally was very important.
This despecialisation process reduces the amount on the surface of cells of a key protein called ACE-2, which is key to coronavirus attaching itself to cells.
But for people with the risky version of the LZTFL1 gene this process does not work as well, and lung cells are left vulnerable to invasion of the virus.