How did they know?
Simple history.
“I thought I would bring that perspective [of my experience in five
administrations] to the topic today, [which] is the issue of pandemic
preparedness. And if there’s one message that I want to leave with you
today based on my experience … [it] is that there is no question that
there will be a challenge to the coming [Trump] administration in the
arena of infectious diseases … both chronic infectious diseases in the
sense of already ongoing disease … but also there will be a surprise
outbreak, and I hope by the end my relatively short presentation you
will understand why history, the history of the last 32 years that I’ve
been the director of the NAIAD, will tell the next administration that
there’s no doubt in anyone’s mind that they will be faced the
challenges that their predecessors were faced with.”
~ Anthony Fauci, 2017
During the Obama administration ALONE: H1N1, Zika, Ebola (Africa).
It always helps to view things in a fuller context rather than through the spoon-fed, distorted snippets preferred by some media outlets pretending to be semi-objective "news". Who, as it turns out, are now alleging that Anthony Fauci is not to be believed, trusted or lent any credence because........he's not an elected official. Always better to implement political solutions to public health issues, yeah?
After all, it's best to call an electrician when your car starts making funny noises under the hood, isn't it?