United States media reports say doctors are dealing with blood clots - a dangerous new complication in some coronavirus patients with severe infections.
"You just watch it clot right in front of you," said Dr Kathryn Hibbert, director of the medical intensive care unit at Massachusetts General Hospital, CNN reported.
Broadway star Nick Cordero, 41, lost his right leg as a result of blood clots as he fights the Covid-19 virus, the Washington Post reported. Blood thinners failed to stop the problem, forcing doctors to amputate.
Embolisms, heart attacks and other problems caused by blood clots have occurred with other patients, Business Insider reported.
"We're driving blindly based on what we call very weak but very compelling data," said Dr Alex Spyropoulos, a blood clot expert in New York.
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.