# Hantavirus: what is it? Definition, transmission, severity > A hantavirus is an RNA virus carried by wild rodents. Rare but severe in humans. Definition, transmission routes, clinical forms and key figures verified against WHO, ECDC, CDC sources. Published on May 24, 2026 on HantaTracker Canonical source: https://hantatracker.fr/en/articles/what-is-hantavirus/ Category: Comprendre The word **hantavirus** came back into the news with the MV Hondius expedition cruise episode in May 2026. The virus involved, the **Andes virus**, is one of the most severe hantaviruses for humans. But what exactly is a hantavirus? Where does it come from, how does it spread, and is it something to worry about day-to-day? This article answers the essential questions, based on data published by the **World Health Organization (WHO)**, the **European Centre for Disease Prevention and Control (ECDC)** and the **Centers for Disease Control and Prevention (CDC)**. ## Definition: a virus from the animal kingdom A **hantavirus** is a virus of the *Orthohantavirus* genus, in the *Hantaviridae* family and the *Bunyavirales* order. It is a **segmented RNA virus** (three segments coding respectively for the nucleocapsid, the envelope glycoproteins and the polymerase). Several dozen species are currently recognised, only some of which are known to cause human disease. Its main feature is that it naturally infects **wild animals** — chiefly rodents, sometimes bats and shrews — without causing apparent disease in them. The infection is chronic and asymptomatic in the animal host. But when the virus crosses to humans, it can cause severe and sometimes fatal illness. ### A long co-evolution with rodents Each hantavirus strain is generally **closely tied to a host species**. Hantaan virus lives in the striped field mouse in Asia, Puumala virus in the bank vole in Europe. The Andes virus, for its part, is carried by the *colilargo* (*Oligoryzomys longicaudatus*), a rodent of the Andean Cordillera. This specificity is the result of co-evolution over millions of years. The rule has a practical consequence: **the geographical distribution of human hantavirus diseases mirrors that of the reservoir rodents**. Temperate and cold regions with dense forest-rodent populations are the most exposed: East Asia, Scandinavia, Argentine and Chilean Patagonia, rural North America. ## How is a hantavirus transmitted? ### The main route: rodent excreta The vast majority of human infections follow the same scenario: a carrier rodent sheds the virus in its **urine, faeces and saliva**. When a human disturbs these materials — sweeping a closed room dry, vacuuming an abandoned cabin, cleaning an attic — fine particles (aerosols) are put into suspension and can reach the pulmonary alveoli if inhaled. This is why the **CDC explicitly recommends** never sweeping dry or vacuuming a space that may be contaminated by rodent droppings. The recommended method is to spray a diluted bleach solution (1 part bleach to 9 parts water), let it sit for 5 minutes, then wipe with paper towels. ### One exception: the Andes virus and person-to-person transmission Among the known hantavirus species, **only one is the subject of documented person-to-person transmission**: the Andes virus. This particularity was described in epidemiological studies published in the *New England Journal of Medicine* following the Epuyén outbreak (Argentina, 2018-2019), which highlighted transmission events during close, prolonged contact between a symptomatic person and their entourage. That said, person-to-person transmission of the Andes virus accounts for only a **limited fraction of cases**. It requires **close and prolonged contact** with a symptomatic person — same household, direct care without protection, confined space. It is **not** distance airborne transmission like influenza or COVID-19. ### Routes that do not exist Three misconceptions to set aside: - No transmission via **cooked food** or **drinking water**. - No transmission via **domestic animals** (dog, cat, hamster…). No study has shown that these species harbour the Andes or Sin Nombre virus. - No transmission via **mosquitoes** or other vectors. ## Two clinical forms in humans Depending on the strain involved, hantavirus causes two very different diseases. ### Hantavirus pulmonary syndrome (HPS) **Hantavirus pulmonary syndrome** is the most severe form. It is caused mainly by New World hantaviruses — Sin Nombre virus in North America, Andes virus in South America, Laguna Negra virus in Paraguay. The clinical picture evolves rapidly: a flu-like phase for 3 to 5 days, then respiratory deterioration with pulmonary oedema and cardiogenic shock within 24 to 48 hours. Per the WHO, case fatality of the American form is **commonly between 20 and 40%**, and may reach **50%** in some outbreaks. In the United States, the CDC has recorded **890 cases** of hantavirus disease from the start of surveillance in 1993 through end of 2023, of which about **35%** were fatal. ### Haemorrhagic fever with renal syndrome (HFRS) **Haemorrhagic fever with renal syndrome** is caused by Old World hantaviruses — Hantaan, Seoul, Puumala, Dobrava. It mainly affects the kidneys, with occasional haemorrhagic manifestations. It is the predominant form in Eurasia. The WHO estimates between 10,000 and over 100,000 annual hantavirus infections worldwide, the vast majority of the HFRS form, and notes that China and the Republic of Korea alone concentrate several thousand cases each year. Case fatality varies widely by strain: **under 1%** for Puumala (moderate European form per the ECDC), **10 to 12%** for Dobrava per the ECDC. For Hantaan, the literature reports rates that may reach around 15%. ## The MV Hondius episode in brief The current episode draws international attention because it combines several unusual features: - An **Andes virus** identified by PCR on 3 May 2026 in several patients on an expedition vessel. - **Person-to-person transmission** suspected on board, in a confined setting (149 people over 40 days). - A **complex sanitary logistics**: medical evacuations from Saint Helena and South Africa, disembarkation in Tenerife (Granadilla de Abona port) coordinated by the WHO and the ECDC, repatriation to 10 countries. - According to initial investigation, the **index case may have been an ornithologist passenger** who photographed birds in a Patagonia area where colilargo colonies are reported, before boarding in Ushuaia. This hypothesis remains to be confirmed by the health authorities. As of 11 May 2026, the official tally was **10 confirmed or probable cases and 3 deaths**, with 195 people under active medical follow-up in 12 countries. The WHO assesses the risk to the general population as **low**, despite the person-to-person transmission documented on board. ## Risk to the general public: low As the WHO and ECDC remind us, hantavirus disease remains a **rare zoonosis** at the individual level. The factors that explain the attention paid to the Andes virus do not translate into a pandemic risk: - Person-to-person transmission **requires close and prolonged contact** with a symptomatic person. - Animal-to-human transmission **requires handling of rodent droppings** in a confined space. - The **long incubation period** (estimated by the WHO at between one and eight weeks, that is around ten days to six weeks per the ECDC) gives health authorities time to identify and follow up contacts. - Epidemiologist Antoine Flahault (University of Geneva) has compared the severity of the Andes virus to that of Ebola, while stressing that its epidemic potential would remain limited outside specific situations of close confinement. No protective measures (mask, distancing) are imposed on the general public in connection with the MV Hondius episode. Surveillance focuses exclusively on repatriated passengers and contacts identified via their return flights. ## And what next? Understanding what a hantavirus is also means placing the MV Hondius episode in the long term: **human hantavirus diseases have existed for as long as we have been able to diagnose them** (the 1950s for HFRS in Korea, 1993 for HPS in the United States). They remain rare, geographically constrained by the distribution of reservoir rodents, and have never caused a pandemic. The Andes virus warrants the international surveillance it is receiving today — precisely **because** its capacity for person-to-person transmission is exceptional within the family. The risk assessment for the general public remains, to date, low and stable.