It's a blood clotting problem from what I've heard. This virus is weird. It affects different people very differently. It can adversely affect virtually every major organ in the body. It can cause blood clotting. It's possible using ventilators too early is partly to blame, but there was an article in the Washington Post which has a series written by health professionals on the front lines battling this in all sorts of ways. This doctor keeps getting called in to remove blood clots, and then more blood clots form and he has to remove those. Many of these are happening in young people who shouldn't really be having this. But again, this is one bad disease.