The details of the ongoing outbreak of hantavirus may sound uncomfortably familiar to all of us who lived through Covid-19: an aggressive pneumonia-like infection, a cruise ship quarantined with sick passengers, the world’s public health authorities on high alert.

So it’s natural to have the follow-up question: Is this the next pandemic?

Not likely, experts say, for one major reason: Hantavirus is not equipped for rapid transmission in the same way that the novel coronavirus was. “Just because something is a public health emergency doesn’t mean it’s a pandemic,” Amesh Adalja, senior scholar at Johns Hopkins Center for Health Security, told me. Bill Hanage, associate professor of epidemiology at Harvard University, said while it’s vital to stamp out the outbreak, his concerns about a large-scale emergency are “essentially nil.”

But this is still a big deal. Three people have died so far. Five others have gotten sick. Nearly 150 people are trapped on a cruise ship that has been rerouted to the Canary Islands for medical assistance. And if nothing else, the hantavirus poses a test for public health’s ability to quash an outbreak before it gets out of hand.

Here’s what you need to know.

Here is the timeline of events aboard the cruise ship MV Hondius, which departed from Argentina on April 1 with plans to travel to islands across the Atlantic Ocean as even as far as mainland Antarctica, according to the World Health Organization:

As of Thursday, three other people reporting gastrointestinal symptoms and high fever are suspected to have hantavirus and remain onboard the ship, as do 147 passengers and crew who are being quarantined to prevent further spread. Before the hantavirus was identified in early May, at least 30 passengers had already disembarked from the ship, according to CNN. They are now being treated or monitored across the globe, from the US (where asymptomatic patients are being observed in Georgia and Arizona) to the UK to Singapore.

The ship, meanwhile, is on its way to Spain’s Canary Islands and will arrive this weekend. Passengers are expected to be sent home provided they have no symptoms.

Hantaviruses are a group of viruses, with different strains circulating in different parts of the world. The strains found in North and South America can cause serious respiratory illness with a very high mortality rate, and they are usually spread by close contact with rodent feces or urine.

These are a rare but well-documented breed of virus: Gene Hackman’s wife died from hantavirus syndrome in early 2025. There was also an outbreak in the Four Corners area of the southwestern United States in 1993 that sickened more than 30 people, and more than half of them died. There are no existing vaccines or treatments for hantavirus, but early detection and intensive care can lead to better outcomes.

The Andes strain of hantavirus that has infected patients on the MV Hondius circulates in South America, and the first patient is known to have traveled in South America before boarding the cruise ship in Argentina. What’s distinct about the Andes strain is that it is the only known hantavirus that has shown prior evidence of human-to-human transmission, part of the reason that so many lay people are concerned that this could be the start of a much wider outbreak.

But there lies the good news: Even this Andes strain of the hantavirus is not very good at spreading between people. Human-to-human transmission still requires close contact with bodily fluids — not the airborne aerosols that made Covid so difficult to contain indoors.

In other words, it is not a coincidence that the first two cases on the MV Honius were a husband and wife.

“Hantavirus is not Covid. This is very difficult to spread,” Dr. Monica Gandhi, an infectious disease doctor at UC-San Francisco and San Francisco General Hospital, told me. As Adaja explained it, “it’s not a respiratory virus, and pandemics are really the exclusive province of respiratory viruses.”

But this is still a serious situation that requires a rapid response. We have already lost some time: According to the WHO, the first man who became infected and died on April 11 was not tested for hantavirus, delaying a prompt response.

It wasn’t until early May that the hantavirus was identified as the cause of the cruise infections, and now a global contact tracing effort is underway to track down everyone who was on the ship with the infected patients (not including those still stuck there) and anyone they may have come in contact with. One flight attendant has been hospitalized after possibly coming in contact with an infected passenger from the ship, although it has not been confirmed whether she had tested positive for hantavirus.

So it is still possible for this to get worse, even if the risks to most of the population are minimal. “I am anxious that it could take time to chase down the remaining transmission chains,” Hanage told me. He said at this stage the hantavirus emergency is reminiscent of the SARS-1 outbreak in 2002 and early 2003, during which travel-based cases allowed the virus to spread from southern China to more than two dozen countries, eventually infecting more than 8,000 people and killing more than 750.

A worst-case scenario might look more like that than Covid-19 — but that’s still something we should be working to avoid.

Right now, experts say, the priority is treating the patients who are already sick, tracing the contacts of those who have left the ship, and making sure that people who are known to have been in close contact with infected people monitor themselves for symptoms and know to seek medical care if symptoms develop. According to the WHO, hantavirus symptoms usually appear two to four weeks after exposure, although it can take as long as eight weeks.

The rest of the ship’s passengers who have not had close contact with any infected people should be allowed to go home, Adalja said. Given the virus’s nature, their risk of transmission is low.

We do have blood tests for hantavirus, something we did not have at first for Covid, which can detect the virus when symptoms are still mild or non-specific. That would be the ideal response in a situation like this, Gandhi told me: Test people and if they are negative, let them go — with a warning about symptoms to watch out for, just in case.

“This is something that can be done outside of that ship,” Adalja said.

Going forward, Gandhi said, cruise ships could be routinely checked for rodents or signs of the droppings and fluids that can spread hantavirus. Adalja said he hoped to learn more about the initial contact that caused the cruise outbreak: Reporting suggests that the Dutch couple had passed through Argentina, Chile, and Uruguay — including to places where the rats who carry hantavirus are known to live — before becoming sick.

For the rest of us, hantavirus isn’t an immediate threat, but the current emergency is still a learning opportunity, given that this virus can occasionally be found in the US. According to the CDC, you should avoid contact with rodent droppings or saliva, and if they are present in your home, try to clean up after them. Wear gloves when cleaning and use a preferred disinfectant.

It’s only natural to fear the worst after Covid-19 killed millions and shut down the world’s economy for months. But we have a playbook: contact tracing, strategic isolation, and good hygiene. Now we just have to use it.