Andes Hantavirus Outbreak Highlights Need for Effective Response and International Coordination

Starting in early May 2026, reports emerged of an outbreak of Andes hantavirus (Andes virus, ANDV) associated with the cruise ship MV Hondius. As of May 12, 2026, at least eleven cases and three deaths have been associated with the outbreak, including three additional passengers who tested positive after repatriation to France, Spain, and the United States on May 10 [1–5]. Andes virus infection is associated with an estimated fatality rate of 20–40% [6]. The outbreak has involved multiple countries and triggered international public health investigations and contact tracing efforts [1–5].

The outbreak is notable because it involves Andes virus, the only hantavirus with clearly documented person-to-person transmission [6–9].

What is known

The MV Hondius departed from Ushuaia, Argentina, on April 1, 2026, carrying international passengers and crew [1,3]. During the voyage, passengers disembarked at multiple locations including Saint Helena, while additional passengers and crew continued until disembarkation on May 10 [3]. 

Because relatively few transmission events have been characterized in the current outbreak so far, the strongest evidence about Andes virus transmission dynamics comes from prior well-studied outbreaks, particularly the 2018–2019 Epuyén outbreak in Argentina.[9] 

That outbreak involved 34 confirmed cases, 11 deaths, superspreading events, and multiple generations of transmission, with a reproductive number of approximately 2.1 before interventions were implemented [9]. A New England Journal of Medicine study concluded that person-to-person transmission occurred and reported evidence consistent with airborne transmission through aerosolized particles [9].

Factors creating elevated risk

The International Hantavirus Society and members of the international hantavirus scientific and clinical community released a public statement [6] emphasizing several conditions that create elevated transmission risk:

• the precise timing of infectiousness remains incompletely defined
• transmission before clear symptoms may occur
• negative PCR testing early in illness may not reliably exclude infection [12]
• incubation periods may extend to 45 days or longer [6,13].

Together, these factors imply that monitoring exposed individuals alone cannot be relied upon as a sufficient outbreak prevention measure. After infection, the times at which a person becomes infectious, develops symptoms, and tests positive may not occur in the same sequence. Therefore, quarantine and isolation protocols become necessary components of response policy. This necessity arises from the potentially severe consequences of sustained transmission, even if the probability of such spread is not high.

Such measures were successful during the Epuyén outbreak, where isolation, quarantine, and active contact tracing reduced the effective reproductive number to below one [9].

Conditions matter

Researchers involved in the Argentine outbreaks have emphasized that conditions aboard a cruise ship differ substantially from the rural environment where prior outbreaks were studied [10]. Cruise ships involve prolonged indoor shared-air exposure, dense social interaction, and international travel networks [10].

Until now, the primary concern has been transmission onboard the ship itself. Going forward, the central public health concern is transmission associated with the international dispersal of potentially exposed individuals across a wide variety of primarily urban settings during a long incubation period [6,9,10].

Public health implications

The Argentine outbreaks demonstrated that Andes virus transmission chains can be interrupted through isolation, quarantine, contact tracing, monitoring of exposed individuals, and healthcare infection-control measures including respiratory protection [9,10].

There is no evidence that concern about outbreaks leads to harmful public panic. Rather, the evidence supports clear public communication that acknowledges uncertainties, and provides communities with a sense of agency in prevention efforts [14].

Precautionary measures are particularly important because:

• person-to-person transmission is established
• aerosol transmission is biologically and epidemiologically supported
• infectious timing remains uncertain
• testing early in illness may be unreliable
• international dispersal of infected individuals has already occurred and is continuing to occur.

Respiratory protection and airborne precautions

The International Hantavirus Society statement and multiple researchers have emphasized the importance of appropriate respiratory protection [6].

Current WHO guidance inconsistently recommends medical masks in some settings and respirators in others [15]. However, unlike respirators such as N95/FFP2/FFP3 masks, medical masks are not designed to protect against airborne infectious particles. Respirators are already recommended in some national guidance documents for care of suspected Andes virus patients [16] and should become the universal standard of protection.

Recommendations

Based on available information, we recommend that passengers and crew of the MV Hondius, as well as contacts of passengers, be quarantined for 45 days, and that respirators (N95/FFP2/FFP3 or greater) be worn by all healthcare workers and others in contact with suspected or confirmed Andes virus cases.

The recommended quarantine period reflects the established long incubation period of Andes virus infection, which can range from a few days to eight weeks. It also reflects the possibility that infectiousness may occur before symptoms begin or tests become positive.

During the Epuyén outbreak, transmission stopped after quarantine and isolation were implemented. The International Hantavirus Society emphasizes respiratory protection in the context of uncertain infectious timing, test positivity, and possible pre-symptomatic transmission (see also [17]).

We will continue to monitor the progress of the outbreak and share timely information as the matter evolves.

References

1. World Health Organization. Disease Outbreak News: Hantavirus cluster linked to cruise ship travel. May 4, 2026. https://www.who.int/emergencies/disease-outbreak-news/item/2026-DON599
2. Reuters. Two cases of hantavirus linked to ship, South Africa says. May 2026. https://www.reuters.com/business/healthcare-pharmaceuticals/two-cases-hantavirus-which-spreads-human-to-human-linked-ship-south-africa-says-2026-05-06/ 
3. Oceanwide Expeditions. Press updates on MV Hondius outbreak. May 2026. https://oceanwide-expeditions.com/press/press-update-m-v-hondius-8-may-2026-19-00-hrs-cet 
4. AP News. Hantavirus cruise ship outbreak updates. May 2026. https://apnews.com/live/hantavirus-cruise-ship-updates-05-06-2026 
5. Hantavirus-hit ship sets sail for Netherlands as final passengers evacuated in Tenerife. May 2026. https://www.reuters.com/business/healthcare-pharmaceuticals/evacuation-passengers-virus-hit-cruise-ship-be-completed-monday-2026-05-11/
6. International Hantavirus Society. Statement from the International Hantavirus Society and members of the international hantavirus research and clinical community regarding the current Andes virus outbreak investigation. May 2026. https://zenodo.org/records/20075274
7. Wells RM et al. An unusual hantavirus outbreak in southern Argentina: Person-to-person transmission? Emerg Infect Dis. 1997;3(2):171–174. https://wwwnc.cdc.gov/eid/article/3/2/97-0210_article 
8. Padula PJ et al. Hantavirus pulmonary syndrome outbreak in Argentina: Molecular evidence for person-to-person transmission of Andes virus. Virology. 1998;241(2):323–330. https://www.sciencedirect.com/science/article/pii/S0042682297989765 
9. Martínez VP et al. “Super-spreaders” and person-to-person transmission of Andes virus in Argentina. N Engl J Med. 2020;383:2230–2241. https://www.nejm.org/doi/full/10.1056/NEJMoa2009040
10. El País interview with Gustavo Palacios. “Este patógeno es más virulento y puede haber contagios en cadenas.” May 7, 2026. https://elpais.com/ciencia/2026-05-08/gustavo-palacios-experto-en-hantavirus-este-patogeno-es-mas-virulento-y-puede-haber-contagios-en-cadenas.html
11. CNN. Andes strain hantavirus explained. May 2026. https://edition.cnn.com/2026/05/06/health/andes-strain-hantavirus-explained
12. CNN. What the numbers tell us about hantavirus. May 2026 https://edition.cnn.com/2026/05/08/health/hantavirus-by-the-numbers
13. CDC. About Hantavirus. May 2026 https://www.cdc.gov/hantavirus/about/index.html
14. Heino MTJ, et al. From a false sense of safety to resilience under uncertainty. Front Psychol. 2024;15:1346542. doi:10.3389/fpsyg.2024.1346542. https://www.frontiersin.org/journals/psychology/articles/10.3389/fpsyg.2024.1346542/full 
15. WHO Technical note for the disembarkation and onward management of passengers and crew in the context of an Andes virus-associated cluster MV Hondius cruise ship https://www.who.int/publications/m/item/who-technical-note-for-the-disembarkation-and-onward-management-of-passengers-and-crew-in-the-context-of-an-andes-virus-associated-cluster-mv-hondius-cruise-ship.
16. UK Government. Andes virus infection control guidance. https://www.gov.uk/guidance/andes-hantavirus-epidemiology-outbreaks-and-guidance
17. Milton DK, et al. Hantavirus outbreak should reset WHO’s default approach to airborne risk. BMJ. 2026;393:s919. doi:10.1136/bmj.s919. https://www.bmj.com/content/393/bmj.s919