Harlan Krumholz, a cardiologist at the Yale School of Medicine, says he worries about two kinds of long COVID-19.

There’s the obvious version where people suffer prolonged virus symptoms like fatigue, and a stealthier version in which people recover yet carry an added risk of blood clots and strokes.

He doesn’t want to panic people — most of us will probably be fine. But new studies confirm that some will develop an elevated risk of blood clots, strokes or heart attacks. Given that most people have had COVID-19 by now, everyone should be more vigilant about the early warning signs such as chest pain, unusual swelling, numbness, weakness or sudden changes in balance, speech or vision.