They explain step-by-step what is known about how the virus infects the airways, multiplies inside cells, and in severe cases causes the immune defenses to overshoot with a "cytokine storm." This storm is an over-activation of white blood cells, which release too-great amounts of cytokines -- inflammation-stimulating molecules -- into the blood.
"Similar to what happens after infection with SARS and MERS, data show that patients with severe COVID-19 may have a cytokine storm syndrome. The rapidly increased cytokines attract an excess of immune cells such as lymphocytes and neutrophils, resulting in an infiltration of these cells into lung tissue and thus cause lung injury," explains author Professor Daishun Liu from Zunyi Medical University, China.
The cytokine storm ultimately causes high fever, excessive leakiness of blood vessels, blood clotting inside the body, extremely low blood pressure, lack of oxygen and excess acidity of the blood, and build-up of fluids in the lungs ("pleural effusion").