Since the coronavirus first appeared, doctors and researchers have been trying to understand why COVID-19 causes life-threatening illness in some patients, while others have only minor symptoms.
Older patients and those with pre-existing conditions like diabetes, heart disease, and asthma account for many of the ICU admissions, but that doesn’t explain the reports of otherwise healthy people who have become critically ill.
Now, researchers believe some of the most severe coronavirus complications may be caused by an overzealous immune system.
It’s called a cytokine storm — the uncontrolled release of proteins that triggers a massive inflammatory response. This overreaction of the body’s natural immune defense can wreak havoc on vital organs.
“If you had like an apartment building and one room in the apartment catches on fire. The fire alarm goes off, sends a signal,” explains Dr. Christopher Moriates, the Assistant Dean for Health Care Value at the University of Texas at Austin. “The response to that might be to turn on the sprinklers, which is the right reaction. It helps. But if the building turns on the sprinklers throughout the entire building, it's going to cause widespread damage and going to cause harm. Even though the reaction was well-meaning, it was an overreaction”
As the virus infects the lungs, white blood cells rush in to attack it, passing through blood vessels and causing leaks that lead to fluid buildup. The cytokine storm, however, doesn’t only affect the lungs. It often causes the immune cells to attack and inflame other organs including the kidneys, liver, and heart.
These signaling cells also control the body’s clotting function, which means patients experiencing a cytokine storm are more prone to blood clots — putting them at greater risk of heart attack or stroke.
Doctors aren’t sure what causes a cytokine storm in some patients, but researchers at Yale School of Medicine have identified biomarkers that may be an early predictor.
“What we found was that patients who developed severe disease had elevated levels of certain cytokines early during disease, within the first 12 days of symptom onset,” explains Yale School of Medicine Immunobiologist Akiko Iwasaki. “That correlated with mortality as well as a hospital stay length. So we know what those cytokines are. And it may be used as a biomarker to predict who is going to develop severe disease versus who is going to have moderate disease.”
The condition has typically been rare, but experts say it may be a defining feature of severe and critical COVID-19 illnesses.
There is no proven treatment for a coronavirus-induced cytokine storm, but hospitals are closely monitoring patients to see who is at greatest risk for the complications it causes. Anyone who is nursing COVID-19 symptoms at home, should closely monitor any change in symptoms.
Health officials say to call a doctor if shortness of breath or abdominal pain become severe. If you experience dizziness, confusion, or intense nausea, get help immediately.
Researchers are looking for treatments that would target the cytokine storm, preventing the overstimulation of the immune system.
Any potential treatment would not be a cure for the coronavirus, but it could help to reduce COVID-19 fatalities and relieve the burden on hospitals until a vaccine can be developed.