Anthony Fauci, the nation's leading infectious disease expert and member of the Trump administration's coronavirus task force, said he doesn't know why some states still do not have stay-at-home orders in place to stem the spread of the coronavirus.

"Whether there should be a federally mandated directive for that or not, I guess that's more of a political question, but just scientifically, doesn't everybody have to be on the same page with this stuff?" CNN's Anderson Cooper asked the physician during an interview on live television Thursday evening.

"I don't understand why that's not happening," Fauci responded. "If you look at what's going on in this country, I just don't understand why we're not doing that. We really should be."

His comments come after dozens of lawmakers have urged President Trump to issue a nationwide stay-at-home order, which has up until now been up to individual states' discretion. More than 30 U.S. states issued their own orders at varying degrees to limit movement and stem the spread of the outbreak.

Fauci fell short of directly calling for a nationwide stay-at-home order. He remarked to Cooper that "the tension between federally mandated versus states rights to do what they want is something I don't want to get into," but noted the virus will be difficult to contain if some states don't comply by White House guidelines.

Trump said at a White House briefing Wednesday that he does not plan to issue a nationwide order because each state is uniquely affected by the virus.

The same day, Florida Gov. Ron deSantis (R) issued a stay-at-home order after weeks of pressure.

On Thursday, Tennessee Gov. Bill Lee (R), who had been reluctant to put an order in place, did so too after his state was projected to be shorthanded in terms of medical supplies and hospital beds.

"You have to look - you have to give a little flexibility. If you have a state in the Midwest, or if Alaska for example doesn't have a problem, it's awfully tough to say close it down. We have to have a little bit of flexibility," Trump said Wednesday.

Surgeon General Jerome Adams said Wednesday that the White House coronavirus guidelines should be interpreted as a national stay-at-home order.

"My advice to America would be that these guidelines are a national stay-at-home order," he said on NBC's "Today."