Hi Kelly,

Yes, this is something everyone taking care of #COVID19 patients has seen. We still don't exactly which patients will get these blood clots or why, but they're likely leading to a risk of death.

Like everything COVID, there's a lot we don't know. Here's what we do: https://twitter.com/kellyb2076/status/1253139039705870336

COVID likely predisposes patients to these blood clots, especially in the lungs. These clots are frequently seen on autopsy.

We routinely measure blood tests that can suggest whether patients have a higher propensity for these blood clots. These aren't perfect, but are helpful.

Most hospitals have incorporated the use of blood thinners (like heparin) into their treatment algorithms for COVID patients. This is meant to prevent these clots from forming.

We believe that these blood clots may be causing a lot of the death seen in the most severe cases.

I've seen quite a few patients myself with blood clots in their lungs, arms & legs.

But like everything COVID, we don't know exactly WHY this disease causes blood clots in some patients and not others.

And we're not yet in agreement about the best way to prevent or treat them.

Like everything COVID, this is still being studied by many people at many places. Protocols will change in the coming weeks and we'll have a better idea of who is getting these clots & how we can prevent/treat them.

But like so much with COVID, theres a lot we still don't know.

(and I'm glad you copied @ASlavitt on this, because I just listened to his latest podcast episode with @NateSilver538 in which he reminds us all that there is SO much about this disease that we just don't know - add nearly everything about thrombotic complications to the list!)