The Brexit trade deal will face greater challenges ahead as British Prime Minister Boris Johnson is now in intensive care because of the coronavirus, while other key negotiators have either been infected or are in self-isolation.

The U.K. finally left the European Union on Jan. 31, but it remains in a transition period and has a deadline of end 2020 to set a free-trade deal with the EU. Now, whether Britain would be able to meet that deadline is in question.

"In all circumstances it's very difficult to imagine how some sort of large scale trade deal between the U.K. and the EU gets done by the end of the year," Amanda Sloat, a senior fellow at Brookings Institution, told CNBC on Tuesday.

"In the last couple weeks, we've seen EU's Brexit negotiator get coronavirus, the British negotiator has also been showing symptoms and now of course this very sad situation with the prime minister," she added. On March 19, Europe's chief Brexit negotiator Michel Barnier also announced he had been infected, while U.K. negotiator David Frost went into self-isolation around the same time after showing symptoms.

Johnson, 55, was moved to intensive care on Monday as his coronavirus symptoms worsened over the course of several hours, according to a statement from the government. He had announced on March 27 that he tested positive and was experiencing "mild symptoms."

Tweet

Foreign Secretary Dominic Raab will temporarily take over the prime minister's duties while Johnson is hospitalized, the government said.

"Clearly with this move into intensive care, there is a desire to put extra precautions into place, (Johnson) clearly is not in a position to govern at the moment," Sloat said.