So, what could be behind it? Scientists and researchers wonder if the answer could lie in our genes and are beginning to try and understand what differentiates people who get mild cases from those who die.

One possibility is a gene variation in the ACE2 gene. ACE2 is an enzyme that attaches to the outer surface of cells in the lungs, as well as the heart. In an article in Science magazine, Immunologist Dr. Philip Murphy of the National Institute of Allergy and Infectious Diseases said that “variations in the ACE2 gene that alter the receptor could make it easier or harder for the virus to get into lung cells.”

It is also possible that a critical ingredient produced by the body, known as surfactant, which better allows the lungs to expand and contract, becomes depleted in some patients infected with the coronavirus. If you think of your lungs as a sponge, surfactant would be the detergent which would make them soft and pliable. Without surfactant, however, your lung becomes stiff and hard to squeeze. It may be why some patients continue to struggle even on a breathing machine.