At least 23 passengers from the hantavirus-infected cruise ship MV Hondius have already left the boat and returned home, including to the US, according to a shocking new report — and one of them has already gotten sick.

The travelers did not realize that they had been exposed to the deadly virus — which has a mortality rate of up to 40% — when they left the luxury boat during its stop at Saint Helena, a tiny island in the South Atlantic, on April 23, according to a passenger who is still aboard the ship.

“There are 23 people wandering around there, and until three days ago, no one had contacted them,” the passenger told Spanish newspaper El Pais.

“The Australian went back to Australia, the one from Taiwan to Taiwan, the Americans to all corners of North America. The Englishman to England, the Dutch to their homes… I don’t remember the rest.”

On Wednesday, one of those passengers, a Swiss man who had returned home with his wife, came down with hanavirus, authorities said. 

The man was initially taken to a Zurich hospital and tested negative for the virus – which can lie dormant for up to eight weeks. 

He was apparently just one of many expedition passengers who decided to hit the road during the Dutch vessel’s two-day stop in British territory last month.

The passengers were only informed of the terrifying virus outbreak days ago, according to the traveler who spoke to El Pais.

The disease usually spreads by contact with mouse or rat feces or urine — but the World Health Organization suspects that the boat carries a rare strain that spreads human-to-human.

The passenger claimed that the World Health Organization didn’t begin contacting the escapees until three days ago despite the first passenger getting sick on April 6.

That patient, a 70-year-old Dutchman died on April 11 — before the Saint Helena stop.

In Saint Helena, the passenger’s body and his ill wife disembarked — along with the nearly two-dozen other passengers.

The WHO said Wednesday that the ship’s operating company, Oceanwide Expeditions, had recently emailed departed passengers about the “health event” that had overtaken the ship, but didn’t provide a date when that communication began.

Company officials “are currently working on details of passengers and crew who embarked and disembarked on the various legs of the voyage,” an Oceanwide Expeditions spokesperson told The Post in a statement.

“We were in touch with them and kept asking ourselves, ‘When are they going to tell them something?’ Some people weren’t contacted until yesterday,” the passenger said. 

The deceased Dutchman’s wife, who also disembarked in Saint Helena, later succumbed to the virus at a Johannesburg hospital. 

Argentine investigators now believe the couple was responsible for bringing the virus onboard, after picking it up from rodents while visiting a landfill during a bird-watching tour in the city of Ushuaia in mid-March.

However, authorities previously said that the area and the surrounding province of Tierra del Fuego had never recorded a case of the hantavirus.

Hantavirus is usually spread through rodent droppings, but the WHO said one rare strain that can spread between people and carries an alarming 40% mortality rate – the Andes virus – is the culprit behind the outbreak. 

A third passenger has died and at least eight others have become sick with the virus while onboard the 353-foot vessel, which remains anchored off Cape Verde while waiting to port in the Canary Islands. 

On Wednesday, three patients – a 56-year-old British national, a 41-year-old Dutch citizen and a 65-year-old German – believed to be infected with the virus were evacuated from the ship and taken to receive medical attention in the Netherlands.

The WHO didn’t immediately respond to requests for comment.