FAQ
Frequently asked questions about hantavirus, the Andes strain, and the 2026 MV Hondius outbreak.
Hantavirus basics
What is hantavirus?
Hantaviruses are a family of single-stranded RNA viruses (family Hantaviridae) carried by rodents. Different strains cause distinct diseases depending on geography: Old World hantaviruses in Asia and Europe cause haemorrhagic fever with renal syndrome (HFRS); New World hantaviruses in the Americas — including Andes orthohantavirus and Sin Nombre virus — cause hantavirus pulmonary syndrome (HPS). Humans typically become infected by inhaling aerosolised particles from rodent urine, faeces, or saliva. Per the U.S. Centers for Disease Control and Prevention, hantaviruses are not transmitted by mosquitoes, ticks, or contaminated food.
How is hantavirus transmitted?
The primary route is rodent-to-human via inhalation of aerosolised particles from infected rodent excreta. Risk is highest in poorly ventilated enclosed spaces with rodent activity — barns, sheds, agricultural buildings, cabins reopened after winter storage. Direct rodent bites are documented but rare. Of the known hantaviruses, only Andes orthohantavirus has produced verified person-to-person transmission chains, confirmed by whole-genome sequencing during the 2018–2019 Epuyén outbreak in Argentina (Martinez et al., New England Journal of Medicine, 2020). No insect vector has ever been documented for any hantavirus.
What are the symptoms of hantavirus?
Symptoms depend on the strain and the disease it causes. Hantavirus pulmonary syndrome (HPS) from New World hantaviruses, including Andes virus, begins 7 to 39 days after exposure with fever, severe muscle aches (especially in the thighs, hips, and lower back), headache, and fatigue — a prodromal phase that lasts 3 to 6 days and is clinically indistinguishable from severe influenza. The disease then escalates rapidly to breathlessness, pulmonary oedema, hypotension, and cardiogenic shock, with most deaths occurring within 24 to 48 hours of cardiopulmonary collapse. Old World hantaviruses cause HFRS instead, with fever, headache, back pain, and acute kidney injury rather than respiratory failure.
Is there a vaccine for hantavirus?
No vaccine for Andes orthohantavirus or any other New World hantavirus has been licensed in any country as of 2026. Inactivated vaccines against Hantaan virus and Seoul virus are licensed in China and South Korea but offer no cross-protection against Andes virus or other HPS-causing strains. DNA vaccine candidates targeting hantavirus pulmonary syndrome have remained in preclinical and early-phase development at the U.S. Army Medical Research Institute of Infectious Diseases (USAMRIID), with none yet advanced to widespread availability.
What's the difference between HPS and HFRS?
HPS (hantavirus pulmonary syndrome) and HFRS (haemorrhagic fever with renal syndrome) are the two clinical manifestations of hantavirus infection. HPS is caused by New World hantaviruses — Andes, Sin Nombre, Laguna Negra — and affects the lungs and cardiovascular system, with case fatality rates of approximately 30 to 40 percent. HFRS is caused by Old World hantaviruses — Hantaan, Seoul, Puumala, Dobrava — and primarily affects the kidneys. HFRS severity varies widely by strain: Puumala virus is mild (under 1 percent CFR), while Hantaan virus is severe (5 to 15 percent CFR). Different reservoirs, different geographies, different target organs.
Andes virus (the strain)
What is Andes virus (Andes orthohantavirus)?
Andes orthohantavirus (ANDV) is a single-stranded RNA virus in the family Hantaviridae, first characterised after a 1995–1996 outbreak in El Bolsón, Argentina. Its natural reservoir is the long-tailed pygmy rice rat, Oligoryzomys longicaudatus — known locally as the colilargo — which sheds the virus in urine, faeces, and saliva. Andes virus causes hantavirus pulmonary syndrome with a case fatality rate of approximately 35 percent. The virus circulates principally in southern Argentina, Chile, and parts of Bolivia, Paraguay, and Uruguay. Unlike all other known hantaviruses, Andes virus has documented person-to-person transmission.
Why is Andes virus the only hantavirus with documented person-to-person spread?
The biological mechanism is not fully understood. Phylogenetic studies of the 2018–2019 Epuyén outbreak in Chubut Province, Argentina, confirmed person-to-person Andes virus transmission via whole-genome sequencing of acute-phase samples (Martinez et al., New England Journal of Medicine, 2020). Transmission appears most likely during the prodromal phase — the 3 to 6 days of flu-like illness before cardiopulmonary collapse — when patients have the highest viraemia. Hypothesised explanations include differences in Andes virus glycoprotein binding to human respiratory cells, but the question remains active research. No other hantavirus has produced a verified human transmission chain despite decades of global surveillance.
What is the case fatality rate of Andes virus compared to Sin Nombre and Seoul virus?
Case fatality rates vary substantially across hantavirus strains. Andes virus in Argentina and Chile carries approximately 30 to 40 percent mortality per CDC and PAHO surveillance. Sin Nombre virus in the western United States and Canada carries approximately 36 percent mortality per US surveillance. Seoul virus, found worldwide in urban Norway rat populations, carries 1 to 2 percent mortality. Puumala virus in northern Europe carries under 1 percent. Hantaan virus in East Asia carries 5 to 15 percent depending on the surveillance series. Andes and Sin Nombre cause hantavirus pulmonary syndrome with similar lethality; Seoul and Puumala cause much milder HFRS variants.
What is the incubation period for Andes virus?
The Andes virus incubation period is 7 to 39 days, with a median of approximately 21 days. The long upper bound is why public-health quarantine and contact-monitoring periods around confirmed Andes virus cases are typically set at three to six weeks. During incubation, infected patients are asymptomatic and have no detectable signs until the prodromal phase begins. The long incubation also means clinicians evaluating returned travellers may miss the Andes virus link without prompting — disclosing recent travel to endemic regions matters.
Has anyone survived Andes pulmonary syndrome without ECMO?
Yes. Most survivors of Andes pulmonary syndrome through the 1990s and 2000s were treated with mechanical ventilation, vasopressor support, and meticulous fluid management — before ECMO (extracorporeal membrane oxygenation) was widely available. However, mortality is markedly lower when ECMO is initiated early in the cardiopulmonary phase, and the 2018–2019 Epuyén outbreak in Argentina demonstrated improved survival at centres with ECMO access. ECMO is not curative — it bridges the patient through severe pulmonary oedema and cardiogenic shock until the viral phase resolves. Without ECMO, survival depends critically on early ICU admission and aggressive supportive care.
Is ribavirin effective against Andes virus?
No. Ribavirin showed some activity against Old World hantaviruses, particularly Hantaan virus causing HFRS, in studies through the 1980s and 1990s. However, a placebo-controlled, double-blind trial of intravenous ribavirin for hantavirus cardiopulmonary syndrome in North America found no clinical benefit (Mertz et al., Clinical Infectious Diseases, 2004). Ribavirin is not part of standard Andes virus management. There is no approved antiviral therapy for Andes virus infection; treatment is entirely supportive — oxygen, mechanical ventilation, vasopressors, fluid management, and ECMO where available.
The 2026 MV Hondius outbreak
When did the 2026 Andes virus outbreak begin?
The 2026 MV Hondius cluster began with the departure of the Dutch cruise ship MV Hondius from Ushuaia, Argentina, on 1 April 2026. The first confirmed Andes virus cases linked to the cruise were reported in Argentina within weeks of the ship's port-of-disembarkation. The outbreak has since expanded across multiple countries via repatriation of infected passengers and crew, and constitutes the most geographically distributed Andes virus outbreak on record.
Is there a confirmed human-to-human transmission chain in the 2026 MV Hondius outbreak?
Investigations by WHO, CDC, PAHO, and the Argentine Ministry of Health are ongoing. The shipboard setting — shared confined ventilation, sustained close contact among passengers and crew over a multi-week voyage — is highly consistent with conditions under which Andes virus person-to-person transmission has previously been documented, most notably during the 2018–2019 Epuyén outbreak. Genome sequencing of cluster cases is in progress to reconstruct transmission chains and verify whether secondary cases share viral genotypes with primary cases. See the methodology page for how this site classifies confirmed versus reported transmission.
Which countries have reported Andes virus cases in the 2026 outbreak?
Confirmed and reported Andes virus cases have been linked to multiple countries via repatriation of MV Hondius passengers and crew, including Argentina, Chile, and the Netherlands, with additional countries reporting cases as primary sources (WHO, CDC, PAHO) publish. Per-country case counts and direct links to the official source reports are maintained on the Hantatrack live outbreak map, which aggregates from primary public-health authorities only.
Can rapid antigen tests detect Andes virus, or is PCR or serology required?
PCR or serology is required — no rapid antigen test is approved for Andes virus or any other hantavirus. Confirmed laboratory diagnosis uses one or more of: RT-PCR to detect Andes virus RNA from acute-phase blood, plasma, or tissue; ELISA-based hantavirus IgM serology, which becomes positive within 1 to 3 days of symptom onset; or IgG seroconversion between paired acute and convalescent samples. The IgM ELISA is the most common first-line test in clinical settings. In ICU contexts where speed matters, RT-PCR provides faster confirmation but requires specialist laboratory capacity.
Last updated: May 2026
Read next: Hantavirus — Andes Strain · Prevention · Methodology