Hantavirus is suspected of spreading aboard a luxury cruise ship, killing three passengers and sparking new concerns as a once obscure disease, with an extraordinarily high death rate, rises amid changing climate conditions.

Officials are still trying to determine what happened aboard the ship, which commands fares of up to $28,845 for a 46-day journey that includes a tour of the Antarctica Peninsula and stops in Tierra del Fuego on the southern edge of Argentina.

In addition to the three deaths, a fourth passenger was evacuated to a South African hospital and was in intensive care, and two crew members fell ill. The Dutch-flagged ship remained off the coast of Cape Verde, an island nation about 400 miles west of Senegal, where it was scheduled to have docked Monday.

Hantavirus is fairly rare in the Americas, but its high case fatality rate makes it a disease of major public health concern, the World Health Organization says. Hantavirus is more common in Asia and Europe, where the strains that circulate are less deadly, with a case fatality rate that ranges from less than 1% to 15%.

Hantavirus is most commonly spread by inhaling particles contaminated with the virus — such as dried mouse urine, saliva or droppings.

But there is one strain of hantavirus — known as the Andes virus — that can be transmitted from human to human, and has been transmitted in Thailand and Argentina.

It’s unclear what strain of hantavirus hit the ship.

The first death on the ship occurred April 11 somewhere in the Atlantic Ocean, and the man’s cause of death couldn’t be determined on board, the ship operator said. The body was transported off the ship April 24 as the vessel docked on Saint Helena Island, about 1,100 miles off Africa, and the man’s wife accompanied his remains.

The wife became unwell on the trip home and later died. The cruise ship operator was notified of the woman’s death April 27. The couple were Dutch nationals. On the same day, another passenger, a British national, became seriously ill on the ship and was medically evacuated to South Africa. That patient was confirmed to have hantavirus.

A German passenger died aboard the ship Saturday. And on Monday, the ship operator said two crew members — one British, one Dutch — had acute respiratory symptoms, one mild and one severe but both requiring urgent medical care.

Among the possibilities that could explain the suspected outbreak, according to Dr. Peter Chin-Hong, a UC San Francisco infectious diseases expert, are rodents getting on board the ship and exposing people to the virus, or person-to-person transmission.

“Could a cruise member have been cleaning up an area and incidentally aerosolized some rodent droppings?” said Dr. Elizabeth Hudson, regional chief of infectious diseases at Kaiser Permanente Southern California. “Was there a shore excursion that the passengers and crew attended where they were exposed to aerosolized rodent droppings?”

Because hantavirus is so rare, it’s hard to say what effect these deaths might have on the cruise industry. COVID-19 hit the industry hard, but that was a global pandemic with a virus spreading rapidly with human-to-human contact. A key question for investigators is how the virus spread.

The MV Hondius is operated by Oceanwide Expeditions, which has a fleet of four ships and bills itself as a cruise ship eco-tour operator with trips to the Arctic and Antarctica. The MV Hondius can hold 170 passengers in 80 cabins.

As of Monday, there were 148 people on board, including 17 U.S. passengers. One deceased passenger remained on board.

The MV Hondius sailed March 20 from Ushuaia, the capital of Tierra del Fuego on the southern edge of Argentina, on a round trip to the Antarctica Peninsula, returning to port 11 days later. On April 1, the ship left Argentina and headed back to Cape Verde, with stops on the Atlantic Ocean islands of South Georgia, Tristan de Cunha and St. Helena.

The strains of hantavirus in the Americas are attracted to the small blood vessels of the lungs and make the blood vessels leaky — which is bad, because the lungs need air, Chin-Hong said.

“So people can’t breathe,” he said. “It’s like you’re drowning. The lungs are leaky, so the fluid fills up in the lungs.”

There are 50 species of hantavirus. The virus that’s found in the Americas tends to cause a cardiopulmonary syndrome, a condition that affects both the heart and the lungs, said Dr. Gaby Frank, director of Johns Hopkins Special Pathogens Center.

Hantavirus is associated with a case fatality rate of up to 50% in the Americas. It was the cause of death of Gene Hackman’s 65-year-old wife, Betsy Arakawa, in their Santa Fe, N.M., home. Arakawa died days before Hackman, 95, died as a result of heart disease. There were signs of rodent entry in some structures on the couple’s property. Last year, three people in Mammoth Lakes died after contracting hantavirus. There was evidence of mice where all three of the deceased had worked, and one person had numerous mice in their home, according to the public health office for Mono County, home to Mammoth Lakes.

There is no vaccine or specific antiviral medicine for hantavirus. In the Americas, doctors can help infected people by putting them on a life-support machine known as ECMO, for extracorporeal membrane oxygenation, which breathes for the patient by oxygenating the blood. “It’s very, very intensive, and that’s why the fatality rate is so high,” Chin-Hong said.

Some experts expect hantavirus to be more of a concern in the future in some parts of the world due to climate change as rising temperatures are favorable to animals and insects that carry diseases, such as the increase in Lyme disease as the climate becomes more hospitable to the ticks that transmit it.

With rainfall patterns changing as global temperatures warm, “then you would expect that the rodent population will increase with time,” Chin-Hong said. Examples include people being sickened with, and dying from, rat-borne diseases such as leptospirosis after Hurricane Maria hit Puerto Rico in 2017.

In the U.S., there’s an average of 30 hantavirus cases reported a year, a figure that has remained relatively steady. But “there has been more media attention to it,” Hudson said.

Times staff writer Karen Garcia contributed to this report.

Shadow gingerly places one taloned foot, then the other, on Jackie as she hunkers down on the nest.

With Big Bear Lake glittering in the distance, he raises each foot in a kneading motion — evoking a bald eagle massage.

“Somehow, it says everything about their bond,” reads the caption on the 15-second video posted to Facebook.

It looks tender. It looks real.

It isn’t.

The clip is AI-generated.

Jackie and Shadow — made world-famous by a 24-hour livestream — aren’t the only animals falsely depicted in deepfakes. AI wildlife videos have flooded social media platforms like YouTube, Instagram and TikTok, racking up millions of views and likes. Some are whimsical, like a handful of bunnies hopping on a trampoline. Others take a more menacing tone, like a jaguar facing off with a dog in a snowy backyard.

Far from benign, some experts say the videos can skew how people view and even interact with wildlife — potentially leading to perilous encounters. They may also undermine viewers’ growing desire to tune into nature to escape the frenetic rhythms of daily life. Repeated exposure could erode trust in media and institutions generally, with one Reddit user proclaiming, “Can’t even watch real animal videos because 90% of them are AI.” There are also legal implications.

The deception works because the depictions are often hyperrealistic. Even a producer for the Dodo, an animal-centric media outlet, admitted to falling for the bouncing bunnies. Often the videos appear to be ripped from trail or security cameras, enhancing vibes of authenticity. In the competitive economy for people’s attention, the videos can help win looks and likes, potentially driving ad revenue for those who post them.

Megan Brief, a digital marketing coordinator for Natural Habitat Adventures, an ecotourism company, had just returned from Svalbard, a far-flung Norwegian archipelago teeming with polar bears and walruses.

Her social media feed piled up with video after video of polar bear rescues, such as fishermen or scientists hauling a freezing, struggling baby polar bear onto a ship. On board, people snapped selfies with the cub before reuniting it with its mom.

She knew they were fake because she was well-versed in the behavior of the snow-white predators, which are fiercely protective of cubs. As the U.S. Fish and Wildlife Service warns, these “large, powerful carnivores” can easily injure or kill people. It would also be illegal to intervene.

But thousands of commenters took what they saw at face value.

“It shows that you can have this close proximity with wildlife that is not only dangerous to you, but it’s dangerous to the animal,” said Brief, who is also a wildlife photographer. Social media is filled with AI animal rescues of all types.

“That’s everyone’s dream, to be one with all the animals and with wildlife,” she added, “but you have to respect their habitat and their behavior and give them the space that they need.”

On the flip side, she said the videos also can perpetuate myths that predators such as wolves and mountain lions are more dangerous than they actually are. It’s easy to see how videos could inflame heated debates over managing such animals, in California and beyond.

In a paper published last September in “Conservation Biology,” researchers said the videos also can make people think animals are more abundant, or less threatened, than they are. They might donate or volunteer less as a result.

“If the public is unable to distinguish between actual threats to biodiversity and fictionalized narratives, the perceived urgency to act may diminish,” the researchers wrote.

Jenny Voisard, media and website manager for Friends of Big Bear Valley, a nonprofit that operates cameras trained on Jackie and Shadow, said her inbox is overloaded with complaints about AI content. Grifters are nothing new — the nonprofit has long contended with fake accounts — but they’ve evolved with the technology.

People who follow the beloved eagles are fed more content about them by the algorithm, and she said AI rises to the top of the feed. (That seems to explain why this reporter is often served the fakes when opening Facebook.)

“People get very upset when they see someone depicting Jackie and Shadow in an unnatural way or wrong, or when it looks like they could be in danger,” said Voisard. Some clips showed owls and ravens attacking the couple, especially riling up fans.

The nonprofit recently trademarked its name and is in the process of copyrighting its livestream. She said the point is to protect what they create, such as merchandise and a detailed log of what the eagles are up to, from fakers.

However, ownership in the age of AI is fraught. Voisard said their livestream can be copyrighted because it’s not just a fixed camera; humans operate it and make choices, like zooming in.

Kristelia García, a professor at Georgetown Law, said such creative choices do give livestream operators a good claim to copyright. Whether something violates it is another matter.

If someone asks a large language model to create a three-minute video featuring eagles without drawing on copyrighted material, no harm no foul, she said. But if they feed the AI program the nonprofit’s footage and ask it to manipulate it, that could make for an infringement claim.

But would it be worth fighting? “Copyright litigation is really expensive and very unpredictable,” said García, who focuses on copyright law. She suspects that only if a lot of money were at stake would a nonprofit be willing to take the risk.

As for concerns about misinformation, “we don’t really have a legal recourse for, like, ‘You got fooled,’” she said. Famous people enjoy certain protections over their name, image and likeness, but famous animals don’t.

The fake video of Shadow “massaging” Jackie casts the eagles in a positive light. It arguably perpetuates the avian love story that Friends of Big Bear Valley describes in its own posts.

Yet Voisard believes people are increasingly tuning into animal livestreams to escape artificiality. Ironically, AI may drive people toward real nature precisely because it can’t replicate it.

“The livestream isn’t being in nature, but it’s the closest thing that a lot of people get,” she said. “Being outside is the best thing for us and our health and our well-being and making that connection. To me, AI is not that.”