Hantavirus: A Virus Known to Science for Decades — But Still Surprising
§ 01 — Origins & Discovery Hantaviruses were first recognized in Asia. During the Korean War (1950–53), thousands of UN soldiers fell ill with a mysterious haemorrhagic fever with kidney failure. The culprit was eventually identified as Hantaan virus, named after the Hantan River in South Korea, and formally classified in 1985. The family was named Hantaviridae in honour of that discovery. The Americas were thought to be free of dangerous hantaviruses until May 1993, when a cluster of young, healthy people in the Four Corners region of the United States (where Arizona, Colorado, New Mexico and Utah meet) began dying of sudden, severe respiratory failure. Federal and state investigators traced the outbreak to a novel virus carried by the common deer mouse (Peromyscus maniculatus). The virus was named Sin Nombre — Spanish for “without a name” — after local objections to earlier geographic names. The 1993 outbreak was indirectly triggered by an El Niño winter, which brought unusual rainfall to the Southwest. Abundant food caused a ten-fold explosion in the deer-mouse population, dramatically increasing human–rodent contact. Frozen lung samples later confirmed that the disease had actually existed since at least 1959, hiding in plain sight. In 1995, a related but distinct virus was isolated in Argentina and Chile: Andes virus (ANDV). Unlike all other known hantaviruses, Andes can spread — under close and prolonged conditions — from one human to another. This rare ability places it in a category of special scientific and public-health concern, and it is the strain at the centre of the MV Hondius outbreak of 2026. § 02 — Global Prevalence Hantaviruses are a global family. Each strain is tightly bound to one rodent species, and the virus’s geographic range mirrors that of its host. While the Andes strain dominates headlines, hantaviruses collectively infect an estimated 10,000 to 100,000 people per year worldwide. In terms of sheer case numbers, East Asia (particularly China and South Korea) bears the largest global burden through the HFRS kidney-disease strains — but in terms of lethality, the Americas are by far the most dangerous zone, with fatality rates up to 40–55%, compared to under 15% in Asia and Europe. The table below covers the regions where the disease is actively tracked. ⓘ In South America, Argentina and Brazil recorded roughly double their usual lethality in 2025, with case fatality rates of 32% and 55% respectively, according to PAHO reporting. Bolivia and Paraguay saw surges in incidence above long-term averages. § 03 — Transmission Hantaviruses are zoonotic — they live in rodents and spill over to humans. The rodent host carries the virus lifelong, shedding it in urine, saliva and droppings without ever falling ill. Humans are “dead-end” hosts for almost all strains — meaning the virus enters a human but cannot jump onwards to another person, so the chain of infection stops there — except with Andes, where limited human-to-human spread is possible. Research from the 2018 Epuyen outbreak found that Andes patients are most infectious on the day fever begins. During that brief window, even a 90-minute interaction — including a moment near a shared restroom at a birthday party — was enough to transmit the virus to multiple people. After the acute fever phase, infectiousness drops dramatically. Yes — significantly. Heavy rainfall, especially from El Niño events, fuels explosive growth in rodent populations by increasing their food supply. More rodents means more virus circulating in the environment and more human exposure. The famous 1993 US outbreak followed an unusually wet winter. Conversely, dry spells can aerosolise dried droppings more easily, also elevating risk. Temperature and humidity influence how long the virus survives outside a host. § 04 — Clinical Picture The insidious danger of hantavirus is how ordinary it looks at first — a fever, aching muscles, fatigue. The long incubation period (two to six weeks for Andes) means patients often do not connect their illness to any specific exposure. By the time breathing becomes difficult, the disease has frequently moved into its most dangerous phase. In addition to lung damage, Andes virus can cause kidney stress — reduced urine output, electrolyte imbalance, and in severe cases temporary renal failure requiring dialysis. This dual lung–kidney attack reflects how the virus causes blood vessels throughout the body to leak fluid into surrounding tissues. There is no approved antiviral cure for hantavirus anywhere in the world. Treatment is supportive. In South American hospitals — particularly in Argentina and Chile where the disease is most common — physicians rely on: ⓘ A vaccine called Hantavax exists for Northeast Asian strains only (Hantaan / Seoul viruses). No approved vaccine exists for Andes virus or other New World strains as of 2026. § 05 — The MV Hondius Outbreak The expedition cruise ship MV Hondius, operated by Oceanwide Expeditions (Netherlands), became the centre of an unprecedented hantavirus cluster in April–May 2026. A hantavirus outbreak aboard a moving international vessel — with 114 passengers from multiple countries — is considered extremely rare by epidemiologists. On 1 April 2026, 114 guests boarded the vessel in Ushuaia, Argentina. The six-week incubation period means cases could still emerge among former passengers now scattered across Europe (Netherlands, Germany, Switzerland, Spain), the United States (Arizona, California, Georgia, Texas, Virginia), and South Africa. A Dutch flight attendant from a connecting flight was also being tested. Investigators are tracing airline contacts across multiple continents. WHO assesses the public health risk as low due to the need for prolonged close contact for transmission — but stresses vigilance until the incubation window closes. § 06 — Safety The MV Hondius case underlines that travellers — especially those venturing into rural, forested, or wildlife-rich regions of South America — face a non-zero hantavirus risk. These practical measures significantly reduce exposure. No — and context matters enormously here. Covid-19 spreads easily through the air in large droplets and aerosols to anyone nearby. Andes hantavirus requires prolonged, close contact — typically between couples, family members, or caregivers. It does not spread through casual contact, public spaces, or sneezes in crowds. The global R₀ of Andes is far below 1 in typical conditions — meaning that on average, one sick person infects fewer than one other person, so the virus naturally fizzles out rather than multiplying through a population the way Covid-19 or measles does. While the MV Hondius outbreak is scientifically significant, it does not signal the emergence of a new pandemic pathogen. WHO has explicitly assessed the global public health risk as low. The scientific community treats this as a serious localised outbreak requiring careful contact tracing — not as a precursor to a global health emergency. § 07 — Containment The response to the MV Hondius cluster illustrates the standard toolkit for containing hantavirus: isolate symptomatic individuals, protect close contacts, trace and monitor the exposed population, and eliminate rodent sources at the point of origin.Where Hantavirus Strikes Around the World
Region / Country Strain Disease Burden Argentina Andes (ANDV) HPS/HCPS ● 100–200 cases/yr Brazil Araraquara, Juquitiba HPS/HCPS ● High fatality Chile Andes (ANDV) HPS/HCPS ● Southern regions USA Sin Nombre (SNV) HPS ● 15–50 cases/yr Bolivia, Paraguay Various HPS ● Rising recently China, South Korea Hantaan, Seoul HFRS (kidney) ● Thousands/yr Scandinavia, Finland Puumala HFRS (kidney) ● Several thousand/yr Balkans, Germany Dobrava, Puumala HFRS ● Periodic outbreaks Panama, Venezuela Choclo, various HPS ● Rare cases How the Virus Reaches Humans
The Infectious Window
Does Weather Affect Spread?
Symptoms & Disease Progression
Kidney Involvement
Treatment Available in South America
A Scientific Rarity: Hantavirus at Sea
Precautions for International Travellers
Controlling an Outbreak
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