A group of refugees and asylum seekers medically evacuated from Manus Island say they are terrified of contracting the deadly coronavirus while being held in cramped facilities in a Melbourne motel.

More than 1180 health-care professionals have signed a joint letter to the government calling for the men to be released, saying makeshift detention centres like the Mantra Hotel in Preston, where they are being held, represent "a very high-risk environment" for the virus to be transmitted.

The letter, drafted by infectious diseases expert Professor David Isaacs, argues hotel guests are also at risk.

Some of the detainees are pictured in a meeting with guards in narrow communal spaces in the Mantra Hotel.

"At the Mantra Hotel in Preston, an already high-risk environment is compounded by the fact that the hotel is used by airline crews, with personnel constantly coming and going from the hotel," it said.