The virus attacks the lungs, but can lead to complications ranging from kidney failure to seizures to heart attacks.
CNN reports that in patients with severe cases, elevated blood clotting has emerged as another complication. Doctors report an unusual jump in cases involving coronavirus patients.
"The number of clotting problems I'm seeing in the ICU, all related to Covid-19, is unprecedented," said Dr Jeffrey Laurence, a hematologist in New York.
Studies in New York City and the Netherlands also have revealed high rates of blood clotting among some coronavirus patients, CNN said. Doctors still don't know why.
"This virus is affecting the lungs, but it appears to be causing inflammation of the whole body," said Dr Viren Kaul, a pulmonary critical care specialist, ABC News reported.
Similar blood-clotting problems appeared in Sars patients.
Blood clots can cause strokes, heart attacks, kidney problems, lung problems and other potentially deadly injuries.