The team at the Columbia University Irving Medical Center in New York City — one of the hospitals flooded with patients in the spring — went through their own experiences and collected reports from other medical teams around the world.
Their comprehensive picture shows the coronavirus attacks virtually every major system in the human body, directly damaging organs and causing the blood to clot, the heart to lose its healthy rhythm, the kidneys to shed blood and protein and the skin to erupt in rashes. It causes headaches, dizziness, muscle aches, stomach pain and other symptoms along with classic respiratory symptoms like coughing and fever.
"Physicians need to think of COVID-19 as a multisystem disease," said Dr. Aakriti Gupta, a cardiology fellow at Columbia who worked on the review, in a statement. "There's a lot of news about clotting but it's also important to understand that a substantial proportion of these patients suffer kidney, heart, and brain damage, and physicians need to treat those conditions along with the respiratory disease."
Much of the damage wrought by the virus appears to come because of its affinity for a receptor — a kind of molecular doorway into cells — called ACE2. Cells lining the blood vessels, in the kidneys, the liver ducts, the pancreas, in the intestinal tract and lining the respiratory tract all are covered with ACE2 receptors, which the virus can use to grapple and infect cells, the Columbia team wrote in their review, published in the journal Nature Medicine.
"These findings suggest that multiple-organ injury may occur at least in part due to direct viral tissue damage," the team wrote.
Coronavirus infection also activates the immune system. Part of that response includes the production of inflammatory proteins called cytokines. This inflammation can damage cells and organs and the so-called cytokine storm is one of the causes of severe symptoms.
"This virus is unusual and it's hard not to take a step back and not be impressed by how many manifestations it has on the human body," Dr. Mahesh Madhavan, another cardiology fellow who worked on the review, said in a statement,
Blood clotting effects appear to be caused by several different mechanisms: direct damage of the cells lining the blood vessels and interference with the various clotting mechanisms in the blood itself. Low blood oxygen caused by pneumonia can make the blood more likely to clot, the researchers said.
These clots can cause strokes and heart attacks or can lodge in the lungs or legs. They clog the kidneys and interfere with dialysis treatments needed for the sickest patients.
Damage to the pancreas can worsen diabetes, and patients with diabetes have been shown to be at the highest risk of severe illness and death from coronavirus.
The virus can directly damage the brain, but some of the neurological effects likely come from the treatment. "COVID-19 patients can be intubated for two to three weeks; a quarter require ventilators for 30 or more days," Gupta said.
"These are very prolonged intubations, and patients need a lot of sedation. 'ICU delirium' was a well-known condition before COVID, and the hallucinations may be less an effect of the virus and more an effect of the prolonged sedation."
The virus affects the immune system, depleting the T-cells the body usually deploys to fight off viral infections. "Lymphopenia, a marker of impaired cellular immunity, is a cardinal laboratory finding reported in 67-90% of patients with COVID-19," the researchers wrote.
Doctors need to treat all of these effects when coronavirus patients show up in the hospital, the Columbia team said.
There is some good news.
"Gastrointestinal symptoms may be associated with a longer duration of illness but have not been associated with increased mortality," the researchers wrote. Many of the skin effects, such as rashes and purplish, swollen "Covid toes," also clear up on their own.
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