From high desert to high seas: why Hantavirus is back in the conversation
Writer: Noah Armstrong
Editors: Madeline Buhman, Michaela Murphy, Rachel Buckley, Jackie Nguyen
Illustrator: Darci Ott
This summer, news of a hantavirus spreading through a cruise ship rocked the world. Perhaps you, like many, felt that familiar pit in your stomach associated with the 2020 COVID-19 headlines (unless you’re an introvert, in which case maybe a tiny part of you briefly thinks “lockdowns weren’t that bad”). A few sentences into the news report, it becomes clear this isn’t that story— no new pandemic, just a rare rodent‑linked virus popping up in a weird place and being sensationalized in the news. Hantavirus is not the type of virus that typically turns into a pandemic, but this summer’s hantavirus outbreak does offer a great opportunity to understand these rare viruses and why we didn’t need to panic.
What exactly is hantavirus?
Perhaps the better question would be, what are hantaviruses? Hantaviruses are not one single virus but rather a family of viruses known as Hantaviridae. To date, 37 recognized hantaviruses are broadly categorized into New World and Old World groups, reflecting both their geographic distribution, the evolutionary history of their respective hosts, and the types of disease they cause. Fortunately for us, only a small subset of the 37 known hantaviruses can infect humans.
Hantaviruses are small, spherical viruses that carry their genetic code in single-stranded RNA rather than double-stranded DNA like humans. Much like influenza viruses (which cause the flu), hantaviruses have genomes that are segmented into 3 distinct parts which allow them to “shuffle” their genetic code like cards in a deck and rapidly adapt to environmental changes. This genetic shuffling (what scientists refer to as reassortment) can alter how infectious the viruses are, the severity of disease they cause, and even change the hosts they can infect. In fact, reassortment is responsible for some of the most significant influenza pandemics in human history!
How hantaviruses spread — and what they do to the body
Hantaviruses are zoonotic viruses, so unlike influenza or COVID-19, hantaviruses are not typically spread through person-to-person contact. Instead, hantaviruses are transmitted through animal hosts— specifically, through the feces, urine, and saliva of infected rodents. Gross, right? To make matters trickier, infected rodents are asymptomatic carriers, passing the virus along without showing any signs of illness. Most hantavirus infections occur when rodent droppings are aerosolized in a confined space and then inhaled by a human. For example, when cleaning out an old shed.
When a human gets infected by a hantavirus, two major types of disease can occur. In the Americas (where new-world hantaviruses are typically found), the most common disease is Hantavirus Cardiopulmonary syndrome (HCPS) which progresses in two main stages. First, patients experience fever/chills, headaches, nausea, diarrhea, and stomach pain. Then, disease progresses to difficulty breathing, low blood pressure, damaged lung tissue, and fluid buildup in the lungs. In Asia and Europe (old-world hantaviruses), the most common disease is Hemorrhagic Fever with Renal Syndrome (HFRS). Much like HCPS, HFRS begins with fever/chills, headaches, and nausea but it instead progresses to acute shock, vascular leakage, and acute kidney failure.
Hantaviruses have long incubation periods (up to eight weeks!) which, in combination with how rare hantavirus infections are, makes early diagnosis difficult. Although HCPS is more dangerous than HFRS (reaching fatality rates up to 45%), both pathologies can be fatal, and unfortunately, there are no available vaccines or standard treatments for hantaviruses aside from supportive care. The good news is that cases of hantavirus infections are very rare with only 890 laboratory confirmed hantavirus infections in the United States between 1993-2023.
Why are the cruise ship outbreaks making the news?
So why have hantaviruses been making headlines this past summer, and what makes these outbreaks different from outbreaks in the past?
First, the cruise ship outbreak was caused by a new-world hantavirus known as Andes virus (ANDV). This type of hantavirus is abundant in Argentina and Chile, is usually carried by the long-tailed pygmy rice rat, and is the only hantavirus known to be transmitted person-to-person. Although difficult to prove and very rare, it is suspected that person-to-person transmission occurred in the recent cruise ship outbreak.
Second, the cruise ship outbreak made headlines precisely because it is so out of the ordinary. In fact, this is the first recorded maritime outbreak of any hantavirus. While norovirus (a common driver of food-borne illness) outbreaks are not uncommon on cruise ships, an outbreak of an environmental disease found in rodent droppings is highly unusual. Investigators initially blamed rodent stowaways, evidence now suggests an infected passenger brought the virus from land into the ship's close quarters. Regardless of transmission route, controlling this unique outbreak was no small feat for epidemiologists, ultimately prompting hantavirus monitoring across 33 countries.
Utahns don’t have to take a cruise to get acquainted with hantavirus
This summer’s cruise ship outbreak is not the first time hantaviruses have made headlines. A major hantavirus outbreak occurred in the four corners region of the United States (the border of New Mexico, Arizona, Colorado, and Utah) in 1993, ultimately resulting in 17 deaths. The outbreak started in western New Mexico and initially puzzled clinicians when seemingly healthy young adults began to succumb to respiratory infections. After 6 months of investigation, the CDC determined that these fatal respiratory infections were caused by a previously unknown hantavirus, Sin Nombre Virus (SNV). SNV is primarily carried by deer mice and found across western North America, including Utah. Researchers believe the 1993 outbreak of hantavirus arose due to abnormally heavy rain and snow that spring bolstering deer mice populations. So, while spring snowstorms can be great for skiing, they can be quite bad (or good depending on how you look at it) for epidemiologists. With the most recent (non-fatal) case of SNV reported in 2025, hantavirus remains present in Utah to this day.
What this means for the average Utahn
First and foremost, the summer hantavirus outbreak is NOT another pandemic like the COVID-19 pandemic. Andes virus is transmissible person-to-person, but it cannot spread as rapidly as COVID-19 and requires prolonged contact with an infected individual to do so. That said, , there are a few precautions you can take to avoid catching hantavirus (particularly SNV) in Utah: 1) Wear an N95 mask in situations where you may interact with rodent droppings. [Cleaning out an old shed? Wear a mask!] 2) Use wet cleaning methods when cleaning up rodent droppings. Don’t vacuum or sweep as this can aerosolize any hantavirus that may be present. Fortunately, even with hantaviruses’ impressive reassortment capabilities, infections remain rare, and person-to-person transmission almost never occurs. For now, book cruises with confidence, and remember that your biggest threat on a cruise ship is some bad shrimp and a gnarly sunburn!
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