The more we look at the virus, the more bizarre it seems. After a few isolated studies suggested lingering heart problems, larger studies are coming in.

For a respiratory virus, SARS-CoV-2 sure causes a lot of non-respiratory problems. Between diabetes, gastrointestinal problems, and heart issues, the coronavirus has puzzled doctors with its capacity to harm different parts of the body. It’s so bizarre that some have even suggested considering it a blood vessel disease, given the many ways in which it seems to interact with the circulatory system. Now, in addition to short-term concerns, the evidence is also mounting for long-term damage.

It started with a lot of anecdotes connecting COVID-19 infection with myocarditis (inflammation of the heart muscle). ESPN has already been reporting such problems for college athletes for about a month, but evidence suggesting lasting heart damage came even earlier, months ago.

All the way back in March, researchers in Wuhan, the pandemic ground zero, reported a concerning association: out of the 416 patients they tracked, roughly 20% tested positive for proteins indicative of cardiac problems. When they looked at 14 of these patients with an ECG, all of them had abnormal heart rhythms caused by COVID-19. Rather surprisingly, this was the best available information for a few months.

Now, new data is starting to come in — and it’s raising even more concerns.

In one German study, researchers examined the cardiac MRIs of 100 people who recovered from COVID-19, comparing them with images from people who were of similar health but had not been infected. Two-thirds of them recovered at home, while a third required hospitalization. The average age of the patients was 49, and the cardiac MRI was carried out two months after patients recovered from the virus.

Startlingly, the MRI showed structural changes to the heart of 78 of them, while 76 had evidence of a biomarker typically found after a heart attack; 60 had signs of inflammation. For a relatively young patient cohort, this is not something you’d expect to see normally.

Other studies indicated that COVID-19 risk and heart problems go hand in hand and heart damage is not uncommon among healed patients. The connection between the coronavirus and blood clots has also been documented.

While the general picture is still patchy and features many unknowns, the weight of evidence is starting to suggest that lasting heart damage may be on the menu for a substantial part of COVID-19 survivors. It’s not clear how severe or long-lasting the damage is and how many people are affected — but the risk seems to be there. In an editorial accompanying the above-mentioned German study, Clyde Yancy, a cardiologist at Northwestern’s Feinberg School of Medicine, and Gregg Fonarow, a cardiologist at UCLA’s Geffen School of Medicine concluded:

“We are inclined to raise a new and very evident concern that cardiomyopathy and heart failure related to Covid-19 may potentially evolve as the natural history of this infection becomes clearer.”