evidence: In particular, early autopsies showed that Covid-19 was causing blood clots all over the body. Some were fatal: Fowkes says that in the first 17 patients her team autopsied, four had died from pulmonary emboli, blockages in the blood vessels of the lungs. Jeffrey Jhang, a pathologist at Mount Sinai who runs laboratory tests for living patients, had noticed some large clots in blood samples he received early on. As autopsies also demonstrated the pervasiveness of clotting, the team at Mount Sinai decided they should treat Covid-19 patients with blood thinners and regularly test for signs of clotting. [...] Through autopsies, pathologists have also uncovered illnesses that sneak in behind Covid-19. Of the samples his team are analyzing, Hewitt says, about three quarters of patients are actually dying from secondary bacterial infections, rather than from Covid-19 itself. When the immune system is battered from fighting Covid-19, simple bacterial and fungal infections can become fatal. "I’ve got one right now on my desk where the patient was in the hospital for about two days," says Hewitt. During that time, the medical team never realized that the patient had what Hewitt describes as "an overwhelming bronchopneumonia," caused by a secondary infection. [...] These kinds of findings have led more hospitals with the resources to increase autopsies of Covid-19 patients to do so. "My impression from discussions with my colleagues around the country is that more and more centers are realizing that that there is value and importance to doing autopsies on patients with Covid-19," says Stone.