“There are three things this virus is doing that blow me away,” Brooks told me. “The first is that it directly infects the endothelial cells that line our blood vessels. I’m not aware of any other human respiratory viruses that do this. This causes a lot of havoc.” Endothelial cells normally help protect the body from infection. When SARS-CoV-2 invades them, their powerful chemical contents get dumped into the bloodstream, resulting in inflammation elsewhere in the body. The rupture of individual endothelial cells coarsens the lining in the blood vessels, creating breaks and rough spots that cause turbulent blood flow.
The second surprise was hypercoagulability—patients had a pronounced tendency to develop blood clots. This reminded Brooks of Michael Crichton’s 1969 novel, “The Andromeda Strain,” in which a pathogen causes instant clotting, striking down victims in mid-stride. “This is different,” Brooks said. “You’re getting these things called pulmonary embolisms, which are nasty. A clot forms—it travels to the lung, damaging the tissues, blocking blood flow, and creating pressures that can lead to heart problems.” More puzzling was evidence that clots sometimes formed in the lungs, leading to acute respiratory distress. Brooks referred to an early report documenting autopsies of victims. Nearly all had pulmonary thromboses; until the autopsy, nobody had suspected that the clots were even present, let alone the probable cause of death.
“The last one is this hyperimmune response,” Brooks said. Most infectious diseases kill people by triggering an excessive immune-system response; COVID, like pneumonia, can unleash white blood cells that flood the lungs with fluid, putting the patient at risk of drowning. But COVID is unusual in the variety of ways that it causes the body to malfunction. Some patients require kidney dialysis or suffer liver damage. The disease can affect the brain and other parts of the nervous system, causing delirium, strokes, and lasting nerve damage. COVID could also do strange things to the heart. Hospitals began admitting patients with signs of cardiac arrest—chest pains, trouble breathing—and preparing emergency coronary catheterizations. “But their coronary vessels are clean,” Brooks said. “There’s no blockage.” Instead, an immune reaction had inflamed the heart muscle, a condition called myocarditis. “There’s not a lot you can do but hope they get through it.” A German study of a hundred recovered COVID patients with the average age of forty-nine found that twenty-two had lasting cardiac problems, including scarring of the heart muscle.
Even after Brooks thought that COVID had no more tricks to play, another aftereffect confounded him: “You get over the illness, you’re feeling better, and it comes back to bite you again.” In adults, it might just be a rash. But some children develop a multi-organ inflammatory syndrome. Brooks said, “They have conjunctivitis, their eyes get real red, they have abdominal pain, and then they can go on to experience cardiovascular collapse.”