Here's the guy's LinkedIn profile. He has a degree in medical biometry and a PhD in computer science.

https://www.linkedin.com/in/knutmwittkowski

I can't see anything on there that would mark him out as a leading expert on respiratory diseases.

I also notice the videos of him talking about coronavirus on YouTube have a hell of a lot of ads on them. There's a reason why Alex Jones wears a Rolex I suppose.