This is interesting. In spring of 2019, Anna Rothschild of 538 interviewed Dr. Fauci. She asked, what keeps you up at night? This was his reply, which didn't make it into her original article:
The thing I’m most concerned about as an infectious disease physician and as a public health person is the emergence of a new virus that the body doesn’t have any background experience with, that is very transmissible, highly transmissible from person to person, and has a high degree of morbidity and mortality.
Now what I’ve essentially done is paint the picture of a pandemic influenza. Now it doesn’t have to be influenza. It could be something like SARS. SARS was really quite scary. Thankfully, it kind of burned itself out by good public health measures. But the thing that worries most of us in the field of public health is a respiratory illness that can spread even before someone is so sick that you want to keep them in bed. And that’s really the difference.
Boy did he have this one nailed.