For immigration historians and other scholars, the way US President Donald Trump is describing the coronavirus pandemic has a familiar ring.

"This is the most aggressive and comprehensive effort to confront a foreign virus in modern history," Trump said in an Oval Office address Wednesday night. "I am confident that by counting and continuing to take these tough measures we will significantly reduce the threat to our citizens and we will ultimately and expeditiously defeat this virus."

As soon as Trump's words describing a "foreign virus" hit the airwaves, Nükhet Varlik knew she'd heard them before.

"We've had plenty of examples of this in the past. It's mindblowing that this still continues," said Varlik, an associate professor of history at Rutgers University in Newark, New Jersey, and at the University of South Carolina.

"It opens up the ways of thinking about disease in dangerous ways," she said. "Once you open that door...historically we have examples, we know where it goes. And we don't want to go there. I find it extremely dangerous."