FWI: Amid a COVID-19 pandemic, the Executive Branch concentrates power to adequately respond. How does it happen? Is the power relinquished?

This is America-focused but I'm interested of how scenarios in other countries could develop.

Context for where the US is as of 27 February, if you need to get up to speed on current events:

A while back, Trump fired the national pandemic coordinator and defunded the entire pandemic response mission. USA did not have an up-to-date Blueprint for pandemic response and the interim coordinator didn't know the plans in the old Blueprint. Today, Mike Pence was given full presidential power to coordinate all aspects of the pandemic response.

The US hasn't scaled up testing as rapidly as other developed nations so the severity of outbreaks in the United States are unclear. Novel Coronavirus just infected some local northern Californian, and early reports suggest this was a civilian with nothing to do with hospitals. If an outbreak in northern California is occurring, than it's almost certain there are already smaller clusters of infections across many major US cities.