Dr. Anthony Fauci has a warning for young adults who think they will bounce back from COVID-19.

Speaking at an event with the American Society for Microbiology, Dr. Fauci pointed out that many young adults and kids who believe they had a “mild” case of the coronavirus take a significant amount of time to recover from all symptoms.

“We’d better be careful when we say ‘Young people who don’t wind up in the hospital are fine, let them get infected, it’s OK.’ No, it’s not OK,” Dr. Fauci said during the briefing.

He went on to say that those who don’t require hospitalization and are otherwise healthy can end up in bed for two or three weeks with COVID-19, and have residual symptoms for weeks or sometimes months longer.

The country’s top infectious disease doctor said check-ups down the road with patients who supposedly recovered have shown many “have a substantially high proportion of cardiovascular abnormalities, evidence of myocarditis by MRI and PET scans, evidence of emerging cardiomyopathies.”

He called these findings “really troublesome” because they are constantly evolving as the world learns more about COVID-19 and the long-term impacts on the human body.