Americans who were on board the cruise ship where a hantavirus outbreak killed three people will finally be allowed to leave quarantine on Monday, but the next few weeks will pose another grueling challenge.

It is unclear how many of the 18 passengers currently being monitored at the National Quarantine Unit in Omaha, Nebraska will be allowed to leave, but those who do will be subjected to three more weeks of isolation in their homes and 24/7 monitoring. 

Federal officials have said that healthcare workers or law enforcement agents will constantly surveil the passengers to make sure they do not leave their homes, which is unusually strict compared to previous efforts to contain the same virus. 

Attorney Steven Hyman, who is representing two of the passengers from New York, told the New York Times that his clients were directly informed of the stringent protocol.

The lawyer told the Daily Mail: 'The major stress for them was just to go home. If the requirement is that they have to isolate themselves, they are willing to do so.'

He added that 'They were beginning to fray, because it’s not the most comfortable in terms of being totally isolated in one room. They wanted to get home, and they were making that clear.' 

It was unclear whether Hyman's clients would be allowed to leave the Nebraska quarantine unit, but New York Health Commissioner James McDonald said late on Friday that they could return home on noncommercial flights and self-isolate until June 22. 

The health commissioner did not address whether the passengers would be constantly monitored.

Hyman told the Daily Mail that his clients expect to return home on Monday and that they will abide by any Centers for Disease Control and Prevention guidelines, though he added: 'I haven't seen any formal order about that. It’s certainly unnecessary.'

Despite some of the 18 passengers being allowed to leave quarantine, others have said that they wish to remain in the unit for the virus's full 42-day incubation period in case they get sick and develop symptoms. 

The passengers have already spent nearly three weeks in isolation. They were brought back to the US from the Canary Islands on May 11, and they have been monitored at the only federally-funded quarantine unit in the country since then. 

None of the passengers have developed symptoms or appear to have the disease. 

At least two passengers were ordered to remain in the Nebraska quarantine unit until at least Sunday, which marked the end of the 21-day period when symptoms are most likely to emerge. 

The orders came from Interim Centers for Disease Control and Prevention Director Jay Bhattacharya after the passengers made plans to return home and self-isolate, which they were initially told they would be allowed to do after testing negative for the disease.

During a similar outbreak of the same Hantavirus strain in 2018, patients were allowed to self-isolate in their homes for 42 days and monitor themselves with regular check-ins from healthcare workers. None got sick. 

Caitlin Rivers, an epidemiologist and professor with the Johns Hopkins Bloomberg School of Public Health, told the New York Times that 24/7 monitoring is unusual and overkill. 'I’ve never heard of that, and I don’t think it’s needful,' she said.   

It also appears that at least seven Americans who were onboard the cruise ship but left early are being subjected to different, less strict rules. 

Those individuals took commercial flights back to the US and have been self-isolating in their homes with daily check-ins from healthcare workers in person or through video calls. It is unclear why the protocols for the two groups are different. 

The cruise ship where the virus broke out, a Dutch liner called the MV Hondius, began its trip to Argentina in early April. Two passengers died from the Andes strain of the Hantavirus that month, and a third died in early May. 

Speaking about his clients, Hyman told the Daily Mail: 'This has been a long ordeal for them. All they did was go on a cruise, and they end up on front-page news and at risk of their life. This needs to come to, hopefully, a happy end.

'The next best thing is for them to get home where they will be comfortable.'

Hantavirus is rare and carried by rodents. It usually does not transfer between humans, but the Andes strain in particular can be transmitted between people who had close contact. 

The CDC has said that there have been no confirmed cases of the virus in the US connected to the cruise ship outbreak. 

The Daily Mail has reached out to the CDC for comment.