At present we are only guessing and grabbing at straws of information, see WHO chief warns 'we are in uncharted territory' as number of coronavirus cases worldwide passes 90,000.
I heard a portion of Dr. Jeff Duchin's remarks at a news conference yesterday. He is King County's epidemiologist, who I know well and respect greatly. He sounded "very uncertain" about the outbreak in King County/Washington state and the right path forward — exactly for the reasons I mention above and are alluded to in the title of the linked story above.
To sum it all up, we don't know, what we don't know. In medicine, that is a science, we expect there to be some definitive answers to our questions. In this instance, those answers are not known yet.
Lastly, I don't understand the WHO's reluctance to declare this disease a pandemic — NOW! But I think that will be forthcoming very soon.