Close to a hundred Australians stuck on MV Greg Mortimer, an expedition cruise ship off Uruguay may be “sitting ducks” as fears of coronavirus outbreak spread.

Already one passenger has been tested positive to COVID-19 and nine others have developed symptoms according to an SBS report.

The passenger with COVID-19 is “in a critically ill condition” but receiving the “best care possible” in a Uruguayan hospital, according to a letter to passengers by Aurora Expeditions managing director, Robert Halfpenny.

The ship, operated by Aurora Expeditions, has been stranded in Montevideo for almost two weeks.

The ship’s doctor and at least three crew members are among those who developed fevers, Mr Halfpenny said. Another three unwell people have since been identified with symptons.

“While we have enormous assistance and understanding of the situation, it will not be clear cut – but we and the governments working with us know that we must find a way to get you off the ship as soon as possible,” Mr Halfpenny said in the letter.

Family members of the 96 Australians on board said they are growing increasingly anxious about the safety of their relatives, many of whom are considered vulnerable to COVID-19, said the SBS report.

Nicholas Bennett told SBS News he was extremely concerned for his parents, Phil, 77, and Elesa, 72, who were on a “trip of a lifetime” when the pandemic hit and are now trapped on the ship.

“They’re pretty much sitting ducks now,” Mr Bennett said. “My father is pretty old, he’s in his 70s and they are high risk so I’m very worried about them,” he said.

The Bennetts left Sydney on 11 March, two weeks before the Australian government moved to ban people from travelling overseas.

Another passenger from Coffs Harbour, Christine Lefeaux Waites told ABC: “I am scared and want to go home. Morale is low and passengers do not even speak to each other. We can go on our balconies for fresh air but other than that no exercise”

Mr Halfpenny said in the letter that there would be comprehensive testing of all healthy passengers but warned it would be difficult to “maintain the same standard of essential services on board” due to the ill health and isolation of the crew.

A second Antarctic cruise ship, the Ocean Atlantic with about 120 Australians on board was allowed to dock at Montevideo port earlier this week and all Australian and New Zealand passengers have since flown out of Uruguay on chartered or commercial flights.

The passengers were allowed to disembark after undergoing health checks said the ship’s operator Chimu Adventures.