The Hantavirus: Everything We Know So Far

Eight cases of Andes hantavirus have been confirmed or suspected among passengers and crew of the MV Hondius — a 353-foot Dutch-flagged expedition cruise ship operated by Oceanwide Expeditions. Three passengers (a Dutch husband-and-wife couple and a German national) have died. Seven additional passengers and crew are sick or under observation, including a KLM flight attendant in Amsterdam UMC who had brief contact with a Dutch passenger who collapsed at Johannesburg's O.R. Tambo airport on April 25.

The ship departed Ushuaia, Argentina on April 1 with 88 passengers and 59 crew, voyaging through Antarctica, Tristan da Cunha, Saint Helena, and Cape Verde before being granted docking permission by Spain on May 6 — at Granadilla, Tenerife in the Canary Islands. Three patients have been medically evacuated for treatment.

Investigators believe the initial exposure occurred in Argentina before the cruise departed, and that subsequent person-to-person transmission accelerated the cluster on board. Andes hantavirus is the only hantavirus documented to spread between humans.

Hantaviruses have been a known human pathogen for roughly 75 years. Three milestones explain how the medical community arrived at the framework currently being applied to the MV Hondius cluster.

1950s — Korean War. More than 3,000 U.N. soldiers fall ill with what is later named Hantaan virus, after the Hantan River. The Hantaan strain (Old World) defines the original Hemorrhagic Fever with Renal Syndrome (HFRS) presentation: fever, headache, low blood pressure, and acute kidney injury. Case fatality 1–15%.

1993 — Four Corners outbreak (U.S. Southwest). A previously unknown disease kills more than half of those infected. The pathogen, Sin Nombre virus, is traced to deer mice and gives the world its first encounter with Hantavirus Pulmonary Syndrome (HPS) — a New World presentation distinct from HFRS, dominated by pulmonary edema and cardiogenic shock. Case fatality ~38%.

1995–1996 — Andes virus identified in Patagonia, Argentina. A cluster in El Bolsón documents person-to-person transmission for the first time. Andes hantavirus remains the only hantavirus known to spread between humans. Subsequent Patagonian outbreaks (notably 2018) have confirmed the pattern: close, prolonged contact (household, hospital ward, shared cabin) is required — not casual proximity.

The MV Hondius outbreak is the largest documented Andes-strain cluster outside South America.

In August 2023, staff at the Queensland Public Health Virology Laboratory in Coopers Plains, Brisbane discovered that 323 vials of live virus samples were unaccounted for. The disclosure was made public by Queensland Health Minister Tim Nicholls in December 2024.

The missing material included approximately 98 vials of Hendra virus, 223 vials of lyssavirus, and 2 vials of hantavirus. The samples appear to have moved when a freezer storing them broke down — without the required chain-of-custody paperwork — and were either destroyed during decommissioning or transferred to other storage with no record. The investigation has not been able to determine whether they were lost, destroyed, or removed.

Queensland Health has stated that no human infections from any of these pathogens have been reported in Australia, and there is no indication the vials were stolen or misused. The lab was ordered to overhaul its chain-of-custody, freezer-failure response, and biosecurity protocols.

The breach is sometimes raised in coverage of the MV Hondius outbreak as a parallel point of public concern, but the two events are unrelated: the Hondius cluster involves Andes hantavirus contracted in South America, not the Australian samples (which are not believed to have left a controlled environment).

Read Substrate's full standalone explainer: [What Happened in Queensland: 323 Live-Virus Vials, a Broken Freezer, and a Year of Missing Paperwork](/article/queensland-virology-lab-323-vials-missing-broken-freezer)

Hantaviruses are a family of zoonotic viruses carried by rodents — primarily deer mice, voles, and South American rats. Different strains cause different syndromes:

Hemorrhagic Fever with Renal Syndrome (HFRS) — Old World strains (Hantaan, Seoul, Puumala, Dobrava). Symptoms: fever, headache, low blood pressure, acute kidney injury. Case fatality: 1–15%.

Hantavirus Pulmonary Syndrome (HPS), aka Hantavirus Cardiopulmonary Syndrome (HCPS) — New World strains (Sin Nombre, Andes, Black Creek Canal). Symptoms: rapid-onset fever, muscle pain, pulmonary edema, cardiogenic shock. Case fatality: ~38%.

The MV Hondius outbreak involves Andes hantavirus, a New World strain that causes HPS. It is the only hantavirus documented to transmit person-to-person, first identified in a 1996 cluster in El Bolsón, Argentina, and since confirmed in repeated Patagonian outbreaks.

Most hantavirus infections occur from inhaling aerosolized rodent excreta — urine or droppings disturbed and breathed in. The classic exposure: cleaning out a barn or cabin where mice have been living. Outbreaks are typically rural, occupational, or seasonal.

Andes hantavirus is the exception. Person-to-person transmission was first documented in the 1996 Argentine outbreak and has been confirmed in subsequent clusters, including Patagonia in 2018. Transmission appears to require close, prolonged contact — household, hospital, or shared cabin — not casual proximity. Cabin proximity on a small expedition cruise meets that threshold; brief encounters in airport terminals do not.

Incubation is typically 1 to 8 weeks after exposure.

Initial (1–8 weeks post-exposure): fever (often above 101°F / 38°C), severe muscle pain, headache, fatigue, nausea, abdominal pain.

Severe (HPS) progression: cough, shortness of breath, chest tightness, racing pulse, low blood pressure. Without intensive care, the lungs flood with fluid in 24–48 hours.

There is no specific lab test that distinguishes hantavirus from other viral illnesses in the early phase, which is why several MV Hondius passengers were initially evaluated for influenza or COVID-19 before testing was redirected. Survival depends almost entirely on access to ICU-level supportive care during the cardiopulmonary phase.

There is no FDA-approved cure. Substrate''s prior reporting catalogued every treatment currently on the table — ribavirin, Andes-virus-specific monoclonal antibodies in development, mRNA vaccine candidates, ivermectin claims, and traditional/natural treatments — and found that the only intervention with consistent evidence of life-saving benefit is supportive ICU care: mechanical ventilation, ECMO when available, careful fluid management, and pressors.

Ribavirin shows modest benefit for HFRS strains when started in the first six days of illness. For HPS — the strain MV Hondius passengers have — clinical trials have not demonstrated benefit. Monoclonal antibody candidates and an mRNA vaccine remain in early-stage research; none are FDA-approved or commercially available.

Claims circulating on social media that Moderna is developing an mRNA hantavirus vaccine are not supported by company statements or SEC filings. Ivermectin has no PubMed evidence base for hantavirus, and the mechanism by which it inhibits other viruses (importin α/β1 nuclear-import disruption) does not apply to hantaviruses, which replicate in the cytoplasm.

WHO is coordinating with Dutch, Spanish, U.K., and Cape Verdean authorities. Spain''s health ministry has cleared the ship for docking at Granadilla on Tenerife. The U.S. CDC is monitoring returning passengers in Arizona, California, Georgia, Texas, and Virginia.

Contact-tracing has been criticized: at least 23–29 passengers left the ship at Saint Helena on April 23 before authorities had formally identified the outbreak, and were not informed of their potential exposure until they had already returned to the U.S., Australia, Taiwan, U.K., the Netherlands, and elsewhere. Several have since been identified and contacted by local public-health authorities.

WHO''s regional director for Europe stated on May 4: "The risk to the wider public remains low. There is no need for panic or travel restrictions." That assessment has held through May 7.

Andes hantavirus does spread person-to-person, but only through close prolonged contact — it does not transmit the way SARS-CoV-2 or measles do. The U.S. records 30–60 hantavirus cases annually under normal conditions; the MV Hondius cluster has not changed that baseline outside the directly exposed group.

Travelers who have not been on the MV Hondius or in close contact with a known case face no measurable elevation in hantavirus risk from this outbreak.