You’re probably safe from the Hantavirus outbreak, but here’s what you absolutely must not do, experts say

The deaths of three passengers on the expedition cruise ship MV Hondius have sparked an international effort to trace passengers and crew exposed to a rare Andean strain of hantavirus. The outbreak has reignited public fears about the virus, which most Americans associate with exposure to rural rodents, and raised troubling questions about whether human-to-human transmission will become more common.

Two scientists working on solving the hantavirus problem, Dr. Scott Pagen, a virologist at the University of California, Riverside School of Medicine, and Dr. Marieke Rosenbaum, a veterinary public health expert at Tufts University’s Cummings School of Veterinary Medicine, both say the same thing: Don’t panic, but take it seriously.

An independent environment on a cruise ship

For most of known history, hantavirus has been a disease associated with rodents in close contact: dusty barns, rat-infested cabins, grain sheds. The strain of Andes virus transmitted by MV Hondius is unusual in that it appears to be spread from person to person. But Pegan said the situation on board was unusual.

“One hypothesis is that the virus accumulates in higher titers in saliva,” Pegan said of blood tests that measure specific antibody concentrations. He compared aspects of it to the earlier COVID-19 strain, which was also named after its own famous cruise ship, the Diamond Princess. As society learned six years ago, cruise ships are a perfect breeding ground for viruses. “Certainly this is going to be a breathing site, so more people could be infected.”

But that doesn’t mean the Andes virus behaves in any way like COVID-19. The mode of transmission Pagan describes is what virologists call nosocomial transmission, which is hospital-acquired or close-contact transmission.

“If a patient shows up at the hospital and they don’t really know what they have, and then no one takes any protective measures, then all of a sudden the health care workers are affected because they are so closely associated with the patient,” he explained.

Cruise ship cabins suffer from the same functional problems, he said. “If they’re not in a small container on a cruise ship, then it’s not going to support its own transmission.”

Rosenbaum, who has been studying urban rats in Boston for more than a decade as part of the Boston Urban Rat Study, agrees.

“The risk of hantavirus spreading from person to person is really low, and this cruise feels like the perfect conditions for it to spread to more people than I thought,” she said. “If these people are home and start to feel sick, they’re probably going to stay home and not have as much contact with other people.”

The real risk is cleaning, not contact

Both researchers emphasized that the risk of hantavirus infection in the general population has not changed as a result of the cruise ship outbreak. The virus still spreads almost exactly the way it always has, via aerosolized particles in rodent urine, feces or saliva.

“You know, you’re not going to be face-to-face with a rat that’s breathing heavily on you,” Pegan said.

Rather, the problem lies in how most of us typically interact with rodents during the cleanup process. “Most of the time, like in the United States, it’s usually because someone is cleaning up an area that’s infested with rats, but maybe they’re not using enough PPE, masks, etc.,” Pegan said. “They’re basically dusting off old rat urine and stuff like that and putting it into the air and then they’re breathing it in.”

“You should be careful if you are cleaning an area that has rodent urine or feces,” Rosenbaum said. “You should wear gloves, you should wear a mask, you should spray the area with water because if you just sweep it, it’s going to aerosolize all the dry particles, fecal and urine particles, and potentially increase your inhalation. “And definitely no vacuuming.

She added that the most dangerous exposures tend to occur indoors: in attics, sheds, basements or any enclosed space, “where ventilation is limited, so you get aerosolization of the material and it has nowhere to go.”

What to do (and what not to do)

Both scientists offered the same short, boring advice: Don’t sweep or vacuum rodent droppings; moisten contaminated areas before cleaning; wear gloves and a mask; ventilate the space; and tell your doctor if you’ve recently traveled to South America and develop a fever and muscle aches.

“If someone comes in and says, hey, I have some muscle soreness and I recently traveled to South America, they’re probably getting a blood test for hantavirus,” Pegan said. The diagnosis is not perfect: it is most reliable more than 72 hours after the onset of symptoms.

Pagen said seeing rats on the street is not a reason to panic.

“That’s really the main way hanta spreads: It’s basically stirring up feces, urine and saliva. Rats will bite you and so on,” he said, but added that unless you’re in the same space as a rat, you’re probably going to be fine.

The ‘evil problem’ of surveillance

While Pegan focused on the molecular mechanisms of the virus and developing vaccines and antibody therapies, Rosenbaum worked on a question that was harder to fund and harder to solve: What is actually circulating in the rodents that live among us?

For more than a decade, she directed the Boston Urban Rat Study, working with the city’s inspection department to test wild Norway rats for pathogens, including leptospirosis, Staphylococcus aureus, influenza A, and hantaviruses. Her team is now completing a paper on hantaviruses in Boston rats.

“It’s a pretty tough problem,” she said of urban rodent control and disease surveillance, “because it requires a lot of collaboration across departments to solve.”

The Norway rat, a brown rat that thrives in nearly every major city in the United States, is the host for Seoul virus, a hantavirus that causes hemorrhagic fever with renal syndrome. “Most of the investigations in the U.S. and Europe have been related to groups of rats raised for research purposes, pets, or pet food,” Rosenbaum said. “Very few studies have actually looked at wild rats. So we don’t really know much about whether it exists.”

Serious cases of hantavirus are rare in humans, she said, but that’s partly because no one pays attention. “You can get infected and have mild symptoms and get over the infection, but never go to a doctor and get a diagnosis.”

The problem is that there isn’t enough money to increase surveillance and research on hantaviruses, in part because the virus has never had a high-profile, large-scale outbreak in the United States.

“The financing landscape in general has changed a lot,” Rosenbaum said. “When it comes to monitoring rats, it can be challenging because people might think, well, we should monitor humans first.” She compared it to West Nile virus surveillance, which is now a routine public health function in cities, but only because there have been outbreaks in the past. “If there was an outbreak of rat-caused hantavirus in New York City, there might be more interest in long-term surveillance, but until then, it might not be of interest to the dollar.”

Monitoring wildlife is also difficult. “For trapping rats, we trap in the middle of the night,” she said. “It takes a lot of effort, a lot of money, a lot of time.”

Pegan, who recently received a $3.4 million NIH grant for his research on the Crimean-Congo hemorrhagic fever (CCHF) virus, a close relative of the hantaviruses in the bunyavirus family, made a similar point about treatment development. “If you’re talking about what is a vaccine, or what is a countermeasure? Well, there really isn’t. It’s just because, we haven’t taken this virus seriously enough to invest billions of dollars to get a vaccine. It’s not that we can’t get a vaccine. It’s just that it’s a matter of prioritizing where we’re spending our dollars and dollars.”

His lab developed a vaccine platform currently targeting CCHF that he says could be adapted for hantaviruses. “We developed a vaccine platform for bunyaviruses. We are now using it for CCHF, but it is just one platform and like other platforms it can be adapted to hantaviruses.” He said the platform can provide protection in just three days: “You can use it on Friday, binge-watch Netflix, and then reopen it to the public on Monday.”

The only existing hantavirus vaccine, Hantavax, “is only effective against Seoul virus and hantavirus, which are older viruses,” Pegan said. “There is no evidence that this is of any benefit in the Andes or anywhere else.” (Rosenbaum published a research paper on the discovery of the Seoul variant of hantavirus in Boston rats, but again calmed fears and said infection with the virus is extremely rare).

Another pandemic is on the agenda

It may not be a hantavirus, but given how social humans are and how viruses evolve, it’s only a matter of time before the world could experience another pandemic.

“I can safely say we have another pandemic in our future,” Pegan said. “Do we know when and where? Our population is increasing. We are moving more into areas where these viruses are present and where these animals are, and that does have consequences.”

It’s a breakdown of boundaries between humans and wildlife, Pegan said, pointing to the same dynamics that led to COVID-19, Ebola and now hantavirus outbreaks. “You’re breaking down the human-wilderness interface, and that’s where you’re going to get these intersectional events, just like with COVID.”

Decades ago, Ebola cases in remote villages might have disappeared on their own. Today, the world no longer works like this. “You’re going to have more of this where people are exposed to this climate and then they jump on cruise ships and jump on planes,” Pegan said. “That’s how we live today.”

He noted that a virology researcher happened to be on the cruise ship as a passenger: Dr. Stephen Kornfeld, who was there birdwatching, once again playing with the line between humans and wildlife. “It’s just going to bring more of this,” Pegan said. The combination of human population growth, encroachment on wildlife habitat, and global travel means more and more frequent spillover events. “Evolution is not tied to, you know, the virus not saying, ‘I will never leave the mouse.'” But that doesn’t mean it won’t start sampling other things if you keep exposing it to it over and over again. “

Rosenbaum said the cruise ship outbreak won’t change the immediate risk profile for Americans, but she hopes cities will take a more serious look at who is most affected. One of the trapping sites for the Boston Urban Rat Study is in the heart of Boston’s opioid crisis, where street encampments directly overlap with rodent activity. “These groups of people are having direct physical contact,” she said. “When we think about the risk of contracting rodent-borne diseases, there are certain groups of people we should consider focusing on.”

This story originally appeared on Fortune.com