Dr. Osterholm is also considered to be overly alarmist by many other authorities in his own field. It's a tricky balance though. He has useful knowledge. It's worth paying attention to him. It's also worth seeing other viewpoints in his field.
For example: He doesn't actually know that COVID19 won't go away with heat--nobody does. Many common colds are caused by a coronavirus, and those infections are highly seasonal and affected by temperature. MERS itself is sensitive to temperature, but maybe not to the temps most of the world sees during a normal spring or summer. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6362578/ (Cross-over transmission of MERS from camels to humans is highest when conditions are colder and drier)