The news of three deaths aboard the expedition cruise ship MV Hondius has sent a ripple of anxiety through global health circles, triggering an international effort to trace passengers and crew exposed to the rare Andes strain of hantavirus. For most people, hantavirus is a distant threat, the kind of thing associated with cleaning out a century-old barn in the rural Midwest or exploring a dusty attic in the mountains. But the events on the MV Hondius have raised a chilling question: is human-to-human spread becoming more common?
The short answer is that you are likely safe. However, the outbreak serves as a stark reminder that the boundaries between human habitats and wildlife are thinning. While the risk to the general public remains low, the way we interact with the rodents in our own backyards—and basements—remains the primary point of danger.
To make sense of the risk, I spoke with two experts working on opposite ends of the problem: Dr. Scott Pegan, a virologist at the UC Riverside School of Medicine and Dr. Marieke Rosenbaum, a veterinary public health expert at Tufts University’s Cummings School of Veterinary Medicine. Their consensus is clear: don’t panic, but do change how you clean your garage.
The Cruise Ship Anomaly
Historically, hantavirus has been a disease of proximity to rodents. You breathe in aerosolized particles from rodent urine, droppings, or saliva, and that’s how the infection takes hold. The Andes strain circulating through the MV Hondius is an outlier because it appears capable of spreading between people. But according to Dr. Pegan, the environment of a cruise ship created a “perfect storm” for this transmission.
Pegan suggests that the virus may build up a higher titer—a higher concentration—in the saliva of infected individuals. When you place those individuals in the confined, recirculated air of a cruise ship cabin, you create a respiratory venue that facilitates spread. He compares the situation to the early days of COVID-19 and the Diamond Princess cruise ship, where the architecture of the vessel acted as an accelerant.
However, Pegan is careful to note that this is “nosocomial” spread—meaning it occurs in close-contact or healthcare settings. If a patient enters a hospital and healthcare workers provide intimate care without proper protection, the virus can jump. In the open air of a city or a suburb, this type of transmission is incredibly rare. As Dr. Rosenbaum notes, if an infected person were at home, they would likely stay in bed, drastically reducing the number of people they expose.
What You Absolutely Must Not Do
While the cruise ship headlines are alarming, the real danger for the average person isn’t another human—it’s the act of cleaning. Most hantavirus cases in the United States occur when someone decides to “spring clean” a rodent-infested area without the proper precautions.
The most dangerous mistake you can make is using a broom or a vacuum cleaner on rodent droppings. When you sweep or vacuum, you aren’t removing the virus; you are aerosolizing it. You are effectively turning dried rodent urine and feces into a fine mist that you then breathe directly into your lungs.
To minimize risk, experts recommend a specific, unglamorous protocol for dealing with rodent-contaminated spaces:
- Never sweep or vacuum: This is the golden rule. Avoid any action that kicks up dust.
- Wet the area first: Spray droppings and nesting materials with a disinfectant or a bleach solution. This “weights” the particles, preventing them from becoming airborne.
- Use PPE: Wear rubber or plastic gloves and a mask (preferably an N95) when cleaning enclosed spaces like attics, sheds, or basements.
- Ventilate: Open all windows and doors for at least 30 minutes before you begin cleaning to ensure fresh air is circulating.
| Action | Risk Level | Safe Alternative |
|---|---|---|
| Vacuuming droppings | High | Wet-mopping with disinfectant |
| Dry sweeping a shed | High | Ventilating and spraying with water |
| Touching nests | Medium | Using gloves and disposable bags |
| Walking past a city rat | Extremely Low | Maintain normal distance |
The ‘Wicked Problem’ of Urban Surveillance
While the Andes strain gets the headlines, there is a quieter threat in our cities. Dr. Rosenbaum has spent over a decade leading the Boston Urban Rat Study, testing wild Norway rats for various pathogens. Her research focuses on the Seoul virus, a hantavirus that causes hemorrhagic fever with renal syndrome.
The problem, she explains, is a lack of surveillance. Most research has focused on lab-bred rats, leaving a massive gap in our knowledge regarding what wild urban rats are actually carrying. Because severe hantavirus cases are rare and mild cases often go undiagnosed, the virus doesn’t attract the same funding as high-profile threats like COVID-19 or West Nile virus.
This funding gap extends to therapeutics. Dr. Pegan notes that there is currently no widely effective vaccine for the Andes strain. While a vaccine called Hantavax exists, it only targets older strains like Seoul and Hantaan. Pegan’s lab is currently working on a vaccine platform for the Crimean-Congo hemorrhagic fever (CCHF) virus—a close relative of hantavirus—which he believes could be adapted to protect against hantaviruses in as little as three days.
The Thinning Line Between Humans and Wildlife
The MV Hondius outbreak is a symptom of a larger trend: the breakdown of the “human-wilderness interface.” As populations grow and we encroach further into wild habitats, we create more opportunities for “spillover events.”
Whether it is a bird-watcher on an expedition cruise or a developer clearing land for a new suburb, the more we overlap with wildlife, the more we sample the viruses they carry. In a globalized world, a virus that once would have burned out in a remote village can now reach a major metropolitan hub in less than 24 hours via a plane or a ship.
For those in vulnerable positions, the risk is even more acute. Dr. Rosenbaum points out that people living in street encampments often have direct, daily physical contact with rodent populations, making them a high-risk group that public health officials often overlook.
Disclaimer: This article is for informational purposes only and does not constitute medical advice. If you suspect you have been exposed to hantavirus or are experiencing fever and muscle aches after traveling to South America or cleaning a rodent-infested area, contact a healthcare provider immediately.
The next major checkpoint in our understanding of urban risk will come with the publication of Dr. Rosenbaum’s latest findings on hantavirus prevalence in Boston’s wild rat populations, which will provide a clearer picture of the “invisible” risk in American cities.
Do you have questions about home safety or wildlife exposure? Share your thoughts in the comments or share this guide with someone planning a spring cleanup.
