Covid-19 
Update:*
Deaths from Covid-19 are due to (1) cytokine storm syndrome and (2) fulminant myocarditis.
During a cytokine storm, an excessive immune response ravages healthy lung tissue, leading to acute respiratory distress and multi-organ failure.
All Covid-19 patients sick enough for hospitalization should be given a serum ferritin blood test.
Elevated serum ferritin values are a good first screening tool for the possibility of a cytokine storm syndrome in sick patients with high fevers.
Treating Covid-19 infected patients with cytokine storm syndrome with IL-6 blockade (tocilizumab) has recently been reported in China with successful outcomes.
Fulminant myocarditis 
has also been reported in patients with Covid-19.
Fulminant myocarditis is primarily caused by infection with viruses. It arises quickly, progresses rapidly, and may lead to severe heart failure or circulatory failure presenting as rapid-onset hypotension and cardiogenic shock, with mortality rates as high as 50%–70%.
Physicians should pay attention not only to the symptoms of respiratory dysfunction but also the symptoms of cardiac injury.