HANTAVIRUS – between pandemic risk and feardemic scenario

The story of the Dutch cruise outbreak unfolded from a little unassuming title to a massive cover story in just over a week, as the ship likely carrying the virus has reached Europe. WHO is trying to calm down spirits and diffuse the panic, although it doesn’t have all the data to fully assess the risks in the current situation created. The virus is not new but it is little known and some of its characteristics make detection difficult. A large number of people of different nationalities mixing for several weeks, some of which left the boat and used different commercial flights to travel to different parts of the world compound the problem – the situation is different from any previous outbreak in the Americas. Finally, the psychological toll for those onboard is likely to be significant, the risk of severe illness and the long isolation period create a proper feardemic scenario, for them and their contacts.

PUBLIC HEALTHHANTAVIRUSHEALTHCAREEPIDEMIOLOGY

Irene Petre

5/10/202616 min read

What is hantavirus and it’s associated disease?

Hantavirus pulmonary syndrome (HPS) is a rare and acute zoonotic disease (whose natural reservoirs are primarily rodents such as long‑tailed pygmy rice rat for the Andes strain, the one present on the MV Hondius cruise ship), with a wide distribution in the Americas and there are about 24 different hantaviruses that can trigger the disease. The Andes strain (ANDV) of the virus is one of the most dangerous, not just because it presents human-to-human transmission but due to its severity of symptoms and high mortality rate.

While rodents are typically asymptomatic, in humans it can cause severe disease. The Andes strain is present typically in Chile, Argentina (particularly in the South) and the US (particularly in the South), but other strains of hantavirus are present across other countries in Latin America and North America.

“The incidence of death among persons with hantavirus pulmonary syndrome associated with ANDV is high and has ranged from 21% to 50% in Argentina” according to a study of an Argentinian outbreak, published in New England Journal of Medicine in 2020 and around 60% death incidence has been documented in Chile, according to Luis Escobar, Assoc. Prof. at the College of Natural Resources and Environment at Virginia Tech University, US.

There is a European and Asian strain of the virus but it tends to cause kidney failure (hemorrhagic fever with renal syndrome - HFRS) and is not documented to present human-to-human transmission. The Andes strain can cause respiratory failure (the dominant presentation is cardiopulmonary, with vascular leakage, pulmonary involvement, and respiratory failure) and can spread from human to human. In fact, there were human-to-human outbreaks documented in 1996, 2011 and 2018-19 in Argentina and Chile.

The study of the 2018-19 outbreak in Epuyen, Argentina (a remote village of c. 2800 inhabitants) was documented by Dr. G. Palacios, a microbiologist at the Icahn School of Medicine at Mount Sinai, NY, US and published in 2020 in the New England Journal of Medicine. The study shows that between November 2018 and February 2019 there were many person-to-person transmissions of ANDV, resulting in 34 confirmed infections and 11 deaths, but of course asymptomatic or mild cases could have gone unnoticed and unreported. Serologic testing, contact-tracing, and next-generation sequencing were used to identify ANDV infections.

The number of cases of hantavirus (across the board, not just the Andes strain, but also other strains that do not present human-to-human transmission and whose mortality is lower) seems to be increasing y-o-y in the Americas according to reports from PAHO, the Pan-American Health Organisation.

In Argentina the hantavirus reported cases were 57 in the year July 2024-June 2025 with a sharp increase to 101 cases in the current July 2025-June 2026 year. In Chile in the calendar year 2025 there were 44 reported cases and so far in less than half a year there are 39 reported cases.

In 2025 eight countries in the Americas Region, mainly in the Southern Cone, have reported confirmed cases of hantavirus pulmonary syndrome (HPS), with an aggregated total of 229 cases and 59 deaths, corresponding to a regional case fatality rate of 25.7%. But in many countries such as Argentina, Brazil, Bolivia, Paraguay the fatality rate has almost doubled in 2025.

How does it spread? Who are super-spreaders?

Human primary infection usually occurs not through rodent bites (although infected rodent bites can of course transmit the virus), but via inhalation of aerosolised particles contaminated with rodent excreta (droppings, urine, saliva). Cuts and scratches from infected objects and surfaces are also a source of transmission, as is skin contact with such surfaces.

Exposure can happen in simple settings like cleaning storage spaces, barns, cabins or any enclosed area where infected rodents could have been present. That is why it is always important to use face masks, gloves and other necessary protection when working in such environments.

Secondary infection (person-to-person) happens through inhalation of droplets or aerosolised virions, typically through prolonged direct contact but it can also happen due to proximity with a subject with high viral load and not just through direct contact, as the Epuyen outbreak has demonstrated.

ANDV typically begins with flu-like symptoms and can rapidly progress to severe to HPS. Mild early signs are fever, myalgia (muscle pain), headache, fatigue, abdominal pain with possibly vomiting and diarrhoea. Non specific early symptoms can last for three to seven days.

Severe disease includes cough, rapidly worsening shortness of breath, pulmonary oedema, shock, abrupt respiratory deterioration with capillary leak and even multi-organ failure. Incubation varies a lot, from 4 to 42 or 45 days after exposure.

Before the discovery of ANDV in 1996, the route of transmission was considered to be strictly zoonotic (animal-to-human), resulting in “dead-end human infections” as is the case mostly with cases of the European and Asian virus strains. However, in 1996, an outbreak of 16 or 20 cases of HPS caused by ANDV occurred in the small city of El Bolsón in Patagonia, Southern Argentina and then expanded to other cities. Molecular and epidemiologic evidence suggested human-to-human transmission. The 2011 outbreak of 5 cases in Southern Chile proved the human-to-human transmission.

It was also discovered that virus variants in the Americas show greater ecological plasticity, meaning rodents can transmit the virus across a broader range of species, including humans.

The 2018-19 Argentinian outbreak started at a birthday party in the Epuyen village, where 100 people were present and one sick individual (who only started to present symptoms on that day) managed to infect 5 other individuals in circa 90 min, without having direct and prolonged contact with all of them. “After a single introduction of ANDV from a rodent reservoir into the human population, transmission was driven by 3 symptomatic persons who attended crowded social events.”

Source: Gustavo Palacios et al, The New England Journal of Medicine, 2020

Very importantly, “the route of infection in secondary cases was possibly through inhalation of droplets or aerosolised virions” and the transmission in over 50% of cases happened during the first day of symptoms (the onset of fever) – but it also happened that was the only day when there was an interaction between the infected subjects. The main spreader at the party infected two people who sat next to him at a table, two people at other tables nearby and one person that he came across in the bathroom, without having direct contact with the person. This matters because it means infected subjects can be highly infectious in the early day or days and transmission does not necessarily require direct contact.

After a month and a half and 18 cases later, local authorities enforced isolation and self-quarantine of possible contacts of infected people, which decreased the median reproductive number (the number of secondary cases caused by an infected person during the infectious period) from 2,12 before the control measures, down to 0,96 after the control measures. Investigations showed that patients with a high viral load and liver injury were more likely than other patients to spread infection. The viral load in patients before isolation was also positively correlated with patient age (r=0.46; 95% CI, 0.14 to 0.70). The median age of the patients was 38 years (ranging from 27 to 58).

Patients with higher levels of interleukin-1β (odds ratio, 2.4; 95% CI, 1.3 to 5.5) or a less pronounced elevation of stem cell growth factor β (odds ratio, 0.27; 95% CI, 0.09 to 0.73) were more likely to be spreaders than nonspreaders found the researchers.

The conclusion of the study was that “regardless of disease severity or the immune response of human hosts, patients with ANDV hantavirus pulmonary syndrome should be isolated and their cases carefully managed. Frontline care workers should use appropriate personal protective equipment to help prevent nosocomial transmission”.

“Researchers need more baseline data on hantaviruses in wild rodents to determine if new outbreaks are driven by viral evolution, environmental changes, or increased human exposure” says Luis Escobar, an associate professor in the College of Natural Resources and Environment at Virginia Tech, and a member of the Pandemic Prediction and Prevention DA.

Overall the WHO, The U.S. National Academy of Medicine and many other international experts warned that the world is still poorly prepared for another pandemic.

Source: BBC articles and analysis

Ecological distribution and richness of HPS reservoirs (host rodent species) in Latin America

Source: A. Townsend Peterson et al, International Journal of Health Geographics, 2018

Is there a treatment?

Currently there is no established treatment, although Moderna reported to have been working on a vaccine from before the start of the outbreak. However their research regards the European and Asian hantavirus (not the Andes one, present in the current MV Hondius ship outbreak) and it is in early stages - even if it passes clinical trials, it is nowhere near commercialisation.

Also some vaccines have been used in China and Korea, but long-term results are not available.

However there are things that doctors can do to help in the moderate to severe (cardiopulmonary) phase of the HPS. If the patient reaches this stage (but not all infected people do, some remain with milder symptoms), immediate ICU transfer becomes necessary, followed by oxygen therapy, including mechanical ventilation if necessary, careful fluid management, vasopressors for shock and possibly extracorporeal membrane oxygenation (ECMO) advanced support that has helped in some previous HPS cases - ECMO for advanced HPS has been used at the University of New Mexico with a 70% success rate if intervention was early according to an article published by R.A. Moore and D. Griffen in 2024.

In the 2018-19 Argentinian cases, patients with severe cases had "hypotension, progressive pulmonary edema, and hypoxia (often resulting in intubation), whereas patients with mild cases received only supplemental oxygen" and "Fatal cases were characterized by severe compromise in hemodynamic function, as evidenced by marked hypotension".

Except for one patient, all person-to-person spreaders of ANDV presented with compromised respiratory function. The overall case fatality rate was 32% (11 of 34 patients) according to the study and the mean time from symptom onset to death was 6.7 days (between 4 and 7 days).

Epuyen village in Argentina where a Hantavirus outbreak in 2018-19 saw 34 people getting sick and 11 dying

What is the current situation with the MV Hondius cruise ship

MV Hondius is a Dutch exploration cruise ship, operated by Oceanwide Expeditions that set sail from Ushuaia, Argentina on the 1st April with over 150 people on board (passengers and crew members, from c. 28 countries) and which is expected to arrive in Spain’s Canary Islands on the 10th May in the morning.

The ship was subject to an outbreak of hantavirus Andes strain from Latin America – the first victim, a 70 y.o. Dutch man died on board on April 11th, his wife, 69 y.o. on April 26th in a hospital in Johannesburg, South Africa and a 3rd passenger, an 80 y.o. German woman died on board on May 2nd. Four more symptomatic passengers have been transferred out of the ship – one remains in a hospital in South Africa and 2 in hospital in Netherlands, while one is understood to have been returned to Germany. In total there are 3 fatalities, 8 confirmed cases of symptomatic passengers and 5 suspected as of 10th May.

The ship has a total capacity of c. 170 passengers and 60-70 crew members and guides. The exact number of people who have been on the ship has not been clarified. Different reports cite a number of c. 30 - 40 who disembarked early (four airlifted as mentioned). Some of them are with symptoms in hospital - confirmed (one in South Africa, one in Switzerland, two in Netherlands, one isolating on a tiny island Tristan da Cunha) and suspected (a flight attendant who in the end tested negative in Netherlands, a person in Spain who also tested negative, a person in France who had symptoms on the secure repatriation flight on the 10th and apparently 2 other unknown crew members).

Although the first passenger died on 11th April he was initially thought to have died of natural causes (he was not tested for hantavirus) – other passengers were allowed to disembark and an outbreak was not formally declared until 4th May. It is not clear if the virus was contracted in Ushuaia, Argentina (despite some popular journals claiming so) or not, since some of passengers, including the couple who died, travelled across Latin America before and stopped in remote areas.

A main challenge for health authorities around the world was to trace c. 32 people (or close to 40, even 50 according to some sources, the exact number is not clear) who disembarked from the cruise ship around 22nd – 24th April, before the outbreak of hantavirus was confirmed and also trace anyone who has come into close contact with them since then.

The WHO is in touch with officials in at least 12 countries who are monitoring citizens that were on the ship and mostly returned home on international flights. Those countries include Canada, Denmark, Germany, the Netherlands, New Zealand, Saint Kitts and Nevis, Singapore, Sweden, Switzerland, Turkey, the United Kingdom and the United States.

According to the BBC, one health expert is reported saying that the outbreak response has been "highly chaotic and uncoordinated" but that "overall there was little general risk to the public".

Contact tracing is also in place for people who came in contact with sick people – South Africa for example has identified 62 people.

Everyone who disembarked from the ship and was traced, who is on the ship and is disembarking on the 10th of May or who was in contact with any of the sick people is expected to face 45 days of self-isolation, it is just not clear in what settings – both home self-isolation and hospital isolation have been vehiculated.

The ship claims there are no symptomatic people on board and they are expected to securely disembark through a special protocol in at Granadilla port in Tenerife, Canary Islands and then be flown to their home countries securely, where they will have to isolate.

MV Hondius cabins vary in size and services - below a Twin Porthole and a Junior Suite

Passengers disembark from MV Hondius in small groups and then board dedicated flight charters, following security precautions (10th May)

Why this story matters and what could have been done differently

More than three weeks had passed between the first death and the outbreak being reported, in which time passengers were free to mingle on the ship and disembark in various locations.

Given that this was an exploratory cruise touching various remote and wild islands, any suspicious death on the ship could have been treated with more caution and some distancing measures be put in place straightaway, while waiting for medical investigations to take place and reach conclusions. Previous experiences show in the eventuality of any virus outbreak (including hantavirus) – social distancing and isolation measures are really effective – in the 2018-19 outbreak in Argentine these measures more than halved the R reproductive factor from 2,12 to 0,96. Additionally only organised and secure disembarkment should be allowed in such cases with no passengers being allowed on commercial flights, even when a clear virus outbreak is not yet confirmed - contact with remote wild nature flora and fauna and any suspicious deaths on board should trigger more security measures.

Although the virus is not as contagious as coronavirus, it is circa 20 to 40 times more deadly. The mortality rate for the Andes strain has been reported between 20% and 60% across various outbreaks. This characteristic is enough to make it a rather high risk incident.

On the positive side we seem to have that this virus is an existing virus (although not very well known) and not a new one, it is a very stable virus (so it is unlikely to mutate fast like coronavirus causing Covid-19 did), its survivability airborne seems to be much lower than that of coronaviruses and once contracted, people only seem to be contagious for a rather limited period of time (maybe 2 - 4 days compared to 10 and even 20 days for coronavirus). Environmental survival, outside the human body, on surfaces seems to be 2 – 3 days only at room temperature.

But we also have a few negatives: apart from the much higher mortality rate, it also has a much higher incubation period (40 to 45 days circa), which makes it significantly harder to detect. Another quirk is that people seem to become contagious 1- 2 days before the onset of symptoms, which also makes it harder to test and contain. During the short contagious period – the transmission person-to-person can happen quite easily and without direct or prolonged contact, as it has been documented especially in the previous outbreak in Argentina in 2018-19. Sometimes the health deterioration is dramatically fast (the Dutch woman disembarked without problems on the 24th and collapsed and died two days later). Finally, scientists do not seem to know exactly how long is environmental survival in low temperatures and dark rooms or on different materials (for example the initial variant of coronavirus would survive c. 8h on human skin, 2- 3 days on plastic and steel, 4-5 days on glass and 4 – 14 days on fabric; later Omicron mutated to survive 8 days on plastic and steel and 21 hours on human skin).

Although the ship claims everyone on board to be asymptomatic, the probability that one of those c. 150 people still on board carry the virus is very high. A probabilistic measurement (based on previous outbreaks, the fact that people were able to socialise in large numbers for several weeks on MV Hondius and the long incubation rate) ran using AI Copilot indicates that there may be around one to seven people infected on board but they may not know it yet and some may not develop acute symptoms.

Although the WHO and other medical bodies tried to de-escalate the situation and reduce panic by saying that the outbreak risk for Europe is very low, the truth is that they did not (and probably still do not) have all the necessary data points to assess all the risks. The virus is little known, highly contagious during a short timeframe, has high mortality rate and previous outbreaks have been small and in uncomparable settings (e.g. much easier to isolate people in a small 2800 inhabitants village in a remote area in rural Argentina or Chile than to contain a few dozen highly mobile international travellers, returning to busy towns and cities).

Medical personnel in PPP, security guards and press representatives await the disembarkment

The human factor and outbreak management

As one of the passengers, a young vlogger from the US, put it - “we are real people, not just headlines” – we must not forget the human factor and the various social contexts, decisions, behaviours, compliance levels etc. that shape the response in such epidemiological emergencies and that can facilitate or reduce the spread of pathogens. A cruise ship with circa 200 people on board, socialising in indoor spaces and in close contact with each other for several weeks (before the outbreak was declared) are significant human factors in this situation and so are the outdoor trips taken by the group in St Helena and other places, embarking and disembarking and mixing with other non - passengers.

But for the past two weeks measures were tighten, people stopped socialising and many of those on board must have lived in fear of the potential hidden virus. Some people would have small cabins where it is difficult to move and exercise. Probably no one is looking forward to the further 42-45 days of isolation, be it at home or in a hospital and stress and anxiety are likely to be high. Isolation in unfamiliar places can cause anxiety, noncompliance and conflict. These are people who paid large sums for a relaxing holiday and ended-up in a "feardemic" scenario (Feardemic is a company producing horror video games).

Apart from the passengers, the population of the Canaries and of Tenerife in particular is on high alert and anxious – even if there is no virus outbreak on the island, tourism could suffer for a few months due to the incident and some bad press.

Thirdly, it remains the cost and effort of tracing, testing and isolating all the relevant contacts of those infected or dead and there may be a few hundred people in total. It is not just logistically difficult but also ethically charged to force these people to leave their jobs and daily commitments and isolate for large periods of time.

Perhaps a better option could have been to divert the ship and all its passengers to a private island or a sparsely populated one (in case of force majeur, perhaps the legal and logistical hurdles could have been bypassed) and isolate them there, by a beach, in less austere conditions and where medical testing and surveillance could have been put in place and carried out in isolation. In case of emergency sick people could have been flown to larger hospitals. Unfortunately there is never an easy solution in such virus outbreak emergencies and lack of resources and bureaucracy can slow down things or make some solutions impossible to apply in practice.

Although the initial handling of the MV Hondius outbreak was not the best, how public health authorities collaborate with scientists, doctors and other implicated organisations in the testing and health assessment, disembarkment, repatriation, isolation and treatment (if necessary) of the people on board the vessel and their contacts remains key, as well as future communication campaigns and future preventative measures on board any expedition vessels or other transportation means.

What is important is for health authorities to understand that prevention really is better than having to track and trace and treat. Early preventative measures (such as not allowing passengers to randomly disembark and spread) are essential - and they cannot be replaced by large track and trace and paranoid surveillance mechanisms later on.

Whilst our healthcare systems in modern societies have improved, treatment for many diseases became widely available, lifespan extended and people thought they (almost) conquered nature. The truth is danger in wild natural habitats abounds and can be hidden to the untrained eye - thus a healthy dose of precaution is always needed.

Note: The human factor in epidemiological outbreaks refers to behaviours, activities, and societal structures that facilitate the emergence, transmission, and spread of pathogens. It encompasses population density, urbanisation, travel, land use, and behavioural responses to disease, often acting as the primary driver of pandemic risks. Understanding these factors is crucial for prevention, as modifying human behavior and infrastructure—rather than just targeting the pathogen—is often the most effective method for controlling epidemics.

One of the many horror photos and messages that have been circulating on social media and some news outlets over the past week, causing more panic than necessary

Some sources:

https://www.nejm.org/doi/full/10.1056/NEJMoa2009040#ap1&uccLastUpdatedDate=2026-01-20%2016%3A06%3A29.751%20%2B0000&rememberMe=true

(https://news.vt.edu/articles/2026/05/andes-hantavirus-outbreak-cruise-ship-expert.html

https://news.vt.edu/articles/2025/04/hantavirus-environmental-factors-influence-distribution-paanwaris-paansri-luis-escobar.html

https://www.linkedin.com/pulse/hantavirus-mv-hondius-why-case-has-drawn-global-levon-abrahamyan-esise/?trackingId=qmesQZqqS16Ek2hL1Na8EA%3D%3D

https://epi.minsal.cl/wp-content/uploads/2025/12/Boletin_Epidemiologico_Hantavirus_SE_52_2025.pdf

https://efe.com/mundo/2026-05-07/chile-casos-hantavirus-2026-aumento-letalidad/

https://www.infobae.com/salud/2026/05/06/hantavirus-en-argentina-se-notificaron-42-casos-en-lo-que-va-del-ano/

https://www.argentina.gob.ar/noticias/salud-sostiene-y-refuerza-la-vigilancia-epidemiologica-de-hantavirus-en-el-pais

https://www.paho.org/sites/default/files/2025-12/2025-12-19-epidemiological-alert-hantavirus-engfinal_0.pdf

https://www.bbc.com/news/articles/c8r8j1l6j0go

https://pubmed.ncbi.nlm.nih.gov/9204298/