Situation at a glance
-- This is the fourth Disease Outbreak News report on the Andes hantavirus outbreak linked to cruise ship travel, following the notification to the World Health Organization (WHO) on 2 May 2026 of severe respiratory illness cases aboard M/V Hondius, a cruise ship.
-- Since the last DON was published on 13 May, three additional confirmed cases were reported, from Canada, the Netherlands, and Spain.
-- The previously reported inconclusive case from the United States of America was subsequently determined to be negative following further laboratory testing and has been removed from the total case count.
-- All cases to date have been passengers or crew members on the ship.
-- As of 27 May, a total of 13 cases, including three deaths, have been reported (case fatality ratio 23%).
-- Eleven cases have been laboratory-confirmed for Andes virus (ANDV) infection, and two are probable cases.
-- Given the long incubation period of up to six weeks, it is not unexpected that cases continue to be reported until the end of the six weeks since last exposure.
-- Through the International Health Regulations (2005) (IHR) channels, National IHR Focal Points (NFPs) have all been informed and are supporting international contact tracing and monitoring efforts.
-- WHO has assessed the risk posed by this event to the global population as low and will continue to monitor the epidemiological situation and update the risk assessment as needed.
Description of the situation
-- On 2 May 2026, WHO received notification from the IHR NFP of the United Kingdom of Great Britain and Northern Ireland (hereafter referred to as the United Kingdom) regarding a cluster of severe acute respiratory illness, including two deaths and one critically ill passenger, aboard the Netherlands-flagged cruise ship M/V Hondius.
-- As of 27 May, a total of 13 cases (eleven confirmed and two probable cases), including three deaths (two confirmed and one probable), have been reported.
-- Since the last Disease Outbreak News was published on 13 May, three additional confirmed cases have been reported among passengers or crew members, one each from Canada, the Netherlands, and Spain.
-- The case in Canada developed symptoms during contact follow-up, whereas the cases in the Netherlands and Spain were identified through routine weekly testing of high-risk contacts during follow-up.
-- The previously reported inconclusive case from the United States of America was subsequently determined to be negative following further laboratory testing and has been removed from the total count on 15 May.
-- All confirmed cases are among people who travelled onboard the M/V Hondius.
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Figure 1. Epidemiological curve of Andes hantavirus cases (n = 13) reported to WHO as of 27 May 2026, 17:00.
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-- Based on currently available information, the working hypothesis is that the first case acquired the infection prior to boarding the cruise, through exposure on land.
-- Investigations are ongoing to elucidate the potential circumstances of exposure and the source of the outbreak, in collaboration with authorities in Argentina and Chile, however, the time between the individual’s visit to Chile and the onset of symptoms exceeds the maximum incubation period.
-- Therefore, based on the information currently available, exposure in Chile can be ruled out.
-- Current evidence suggests subsequent human-to-human transmission onboard the ship.
-- This is also supported by a preliminary analysis of the sequences, which show a near-identical sequence from different cases.[1]
-- This outbreak is being managed through a coordinated international response.
-- This includes comprehensive epidemiological investigations, case isolation and clinical management, medical evacuations, laboratory testing, and international contact tracing, as well as quarantine and monitoring measures.
-- Recommendations are subject to change as new epidemiological and laboratory evidence becomes available, including findings from genetic sequencing.
-- Follow-up and contact tracing for all contacts of hantavirus cases linked to the cruise ship is ongoing. This includes passengers who disembarked in Saint Helena, United Kingdom, on 24 April; Ascension, United Kingdom, on 27 April; Praia, Cabo Verde, on 6 May; and Tenerife, Spain, on 10 and 11 May, the remaining 25 crew members and the two healthcare workers from the Netherlands who disembarked in the Netherlands on 18 May and 23 May. Passengers who travelled on flights who may have had exposure to subsequently confirmed cases have been identified and contacted.
-- High-risk contacts are being quarantined and monitored by local health authorities either in their respective countries or in the ship’s flag country, the Netherlands, or third countries (Table 1).
-- As of 22 May 2026, more than 600 contacts, including 53% high-risk and 47% low-risk contacts, have been identified across 32 countries, territories and areas, and are either under close monitoring or self-monitoring in line with the updated guidance on management of contacts of Andes virus (ANDV) cases from the MV Hondius cruise ship published on 17 May.
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Table 1. Contacts being traced for the Andes hantavirus outbreak on a cruise ship reported to WHO as of 25 May 2026, 17:00.
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Epidemiology
-- Hantavirus disease is a zoonotic viral disease caused by hantaviruses of the genus Orthohantavirus, family Hantaviridae, order Bunyavirales. More than 20 viral species have been identified within this genus.
-- Human hantavirus infection is primarily acquired through contact with the urine, faeces, or saliva of certain species of (specific) infected rodents, or by touching contaminated surfaces.
-- Exposure typically occurs during activities such as cleaning buildings with rodent infestations, though it may also occur during routine activities in heavily infested areas.
-- Human cases are most commonly reported in rural settings, such as forests, fields, and farms, where rodents are present, and opportunities for exposure are greater.
-- Human-to-human transmission has currently only been reported for hantavirus pulmonary syndrome (HPS) associated with Andes virus infection.
-- Andes virus (ANDV) is endemic in South America, with confirmed circulation and human cases reported primarily in Argentina and Chile, and additional cases and related strains identified in Uruguay, southern Brazil, and Paraguay.
Andes virus transmission between humans
-- Based on the available information and the existing observations of the current outbreak, limited human-to-human transmission of ANDV is known to occur.
-- However, no large-scale human-to-human outbreaks have been observed historically,[2] suggesting a low probability of transmission per contact.
-- ANDV circulates in specific species of rodents in the Americas, and there have been many sporadic cases reported in Argentina and Chile that have not led to onward transmission.[3]
-- Clusters of human cases have been reported in multiple past outbreaks and have been typically associated with close and prolonged interactions, often in shared indoor environments such as households.
-- The largest reported outbreak of ANDV was reported in Argentina in 2018-2019,[2] where high viral titres in combination with attendance at large social gatherings or extensive contacts among people were associated with higher transmission.
-- While the available evidence suggests that there are multiple modes of transmission that occur with ANDV, the probability of onward transmission between humans remains low.
-- In this recent outbreak of ANDV infection reported on a cruise ship, human-to-human transmission has also occurred.
-- Considering the ongoing epidemiological studies and environmental sampling after the disembarkation of all passengers from MV Hondius, the exact mode(s) through which human-to-human transmission occurred and their relative contributions are yet to be fully understood.
-- Therefore, at present, WHO is operating under the assumption that ANDV transmission:
° may include contact with an infected individual or contaminated surfaces,
° and/or through-the-air transmission (via direct deposition of infectious respiratory particles onto exposed facial mucosal surfaces--mouth, nose or eyes)
° and/or airborne transmission (via inhalation of infectious respiratory particles).
-- The virus does not exhibit transmission dynamics consistent with highly transmissible airborne pathogens (such as measles).
-- This information is up to date as of 27 May 2026. It will be updated as new evidence becomes available and the understanding of transmission evolves.
-- Using data from the previously documented human-to-human outbreaks in Argentina [2] and the 13 cases so far recorded from the cruise ship outbreak, WHO estimates that the mean incubation period is 22 days, corresponding to a probability of safe release from quarantine of 96% at 42 days, reducing to 91% at 35 days. This reaffirms WHO’s recommendation of 42 days of quarantine for high-risk contacts and self-monitoring for low-risk contacts.
-- Using case incidence data from the ANDV outbreak associated with the cruise ship, the effective reproduction number (Rt) for this outbreak as of 22 May is estimated to be 0.7, where anything less than 1.0 indicates that the spread of disease is declining.
Public health response
-- Authorities from States Parties managing cases and/or contacts, WHO, and partners have initiated coordinated response measures, including:
° Ongoing engagement between WHO and the IHR NFPs of countries managing cases and/or contacts to ensure timely information sharing and coordination of response actions.
° International contact tracing and follow up of contacts is ongoing.
° WHO is requesting regular information sharing and periodic updates from States Parties through IHR channels regarding contact monitoring and the health status of high-risk contacts.
° Epidemiological investigations continue to better define epidemiological links between cases and exposure factors on the ship, as well as to try to understand the potential source of exposure.
-- WHO has developed and published specific technical guidance documents to support response to the event, including:
° Technical guidance on the management of hantavirus onboard ships was shared with States Parties through IHR channels
° Technical note for the disembarkation and onward management of passengers and crew in the context of an Andes-virus-associated cluster;
° Management of contacts of Andes Virus (ANDV) cases from the MV Hondius cruise ship
-- IHR NFPs of affected countries have been in contact about passenger and crew information through established IHR channels for those who were on the ship, as well as on planes where a known case was on board. Nearly 1000 communications have occurred through these established channels.
-- Risk communication coordination and support are being provided to ensure sharing of regular, timely and evidence-based information. WHO has activated three-level coordination and is supporting national authorities in implementing risk-based, evidence-informed public health measures in accordance with the provisions of the IHR and related WHO technical guidance documents.
-- WHO regularly convenes expert calls across laboratory, clinical management, epidemiology, infection prevention and control (IPC), and border health and points of entry domains to facilitate timely experience sharing and coordinated expert support.
-- WHO has supported the streamlining and development of research protocols on the natural clinical history in collaboration with national partner institutions and planned a hantavirus scientific consultation on medical countermeasures.
WHO risk assessment
-- WHO continues to assess the risk for passengers and crew who were onboard the cruise ship as moderate, as individuals exposed prior to the implementation of control measures may still develop illness during the incubation period and should therefore be closely monitored.
-- The risk at the global level is assessed as low for the following reasons:
° Andes virus has demonstrated limited human-to-human transmission in previous outbreaks, typically occurring among close contacts and within household settings, generally requiring prolonged close exposure.
° Transmission can be contained through early detection, isolation of cases, clinical management, and contact management. However, the ship environment presented an increased risk due to close living quarters, shared indoor spaces, prolonged exposure, and frequent interpersonal interactions, all of which likely facilitated transmission.
° Human Pulmonary Syndrome caused by hantaviruses in the Americas, including Andes virus, can have a high case fatality ratio, reaching 40-50%, particularly among elderly individuals and those with co-morbidities. The average age of passengers on board the ship was 65 years old.
° Investigations on the travel history and potential exposures of the first case in the Southern Cone subregion of the Americas are ongoing and suggest possible exposure to rodents during recreational activities. Viral sequencing analyses are also ongoing and are comparing the ANDV strain associated with this outbreak with strains circulating in Argentina and Chile, where the disease is enzootic. The preliminary sequencing analysis for the cases indicates a high degree of genetic similarity amongst sequenced cases —showing no more than one single nucleotide polymorphisms difference per individual – which strongly indicates that the outbreak likely arose from a single zoonotic spillover event, or from a very small number of closely related spillover events.[1]
-- Additional cases may occur among individuals exposed before implementation of containment measures. However, the current response, including quarantine for those who have left the ship and rapid isolation of any new suspect cases and the monitoring of contacts, is expected to limit the risk of further spread.
-- As there is no specific antiviral treatment for HPS, suspected cases require prompt transfer to an adequately equipped emergency department or intensive care unit, where available, for close monitoring and supportive management to improve chances of recovery. Consequently, for remote areas, rapid transfer to a well-resourced healthcare facility is required, which may be challenging under the current conditions.
-- For the general public, including people not exposed on board the ship or through close contact with a confirmed case, the overall probability of infection remains low.
-- Current evidence indicates that human-to-human transmission occurs through close and prolonged contact, and can be effectively limited through early detection, isolation of cases, and contact tracing.
WHO advice
-- WHO advises States Parties involved in this event to continue coordinated public health management efforts related to the management of cases and contacts associated with the affected ship and flights, as well as in countries where cases and/or contacts have been identified.
-- WHO has advised and continues to advise a precautionary approach for management of the outbreak related to the ship, with focus on total containment to minimize the onward risk of transmission to other persons.
-- This strategic decision is guided by:
° To date, most of the evidence of human-to-human transmission shows it has required prolonged close exposure, although it is possible that some highly infectious individuals could infect others through a lower degree of exposure.
° Mode(s) of transmission and which mode is dominant if multiple routes of transmission exist are still uncertain.
° Infection is a result of not only exposure, but the setting and duration where exposure has taken place, how infectious the infected person is, and whether personal protective equipment is used.
-- Although the probability of infection is uncertain, if infection occurs, it can be severe. Currently, there is no specific treatment available and severe disease requires advanced critical care.
-- There is a relatively low burden of additional infection prevention and control measures.
-- At this time, WHO does not recommend any changes to routine activities for the general public. People who were on board the affected ship, or who have had close contact with a confirmed case, should follow national health advice. Guidance may be updated as further evidence becomes available.
-- Recommendations remain dynamic and will be updated as additional epidemiological and laboratory evidence, including genetic sequencing data, becomes available.
Coordination
-- WHO advises States Parties involved in this event to continue public health coordination related to the management of cases and contacts in countries where they are present or expected to return, as well as of affected conveyances, as applicable and in close coordination with travel and transport authorities, conveyance operators, and other relevant stakeholders at points of entry.
-- Coordination should ensure the implementation of risk-based, evidence-informed public health measures.
Surveillance
-- Ongoing epidemiological investigations include detection, investigation, and reporting of suspected cases, as well as contact tracing and monitoring.
-- As a precautionary measure, high-risk contacts should undergo active monitoring and home or facility quarantine for 42 days following their last exposure.
-- Current evidence does not support routine laboratory testing or quarantine of low-risk contacts; instead, they should undertake passive self-monitoring and seek medical evaluation if symptoms develop.
-- Contact tracing and listing should utilize all available information sources, including interviews and relevant conveyance-related documentation (passenger manifests, passenger locator forms, and other relevant activity logs), to ensure completeness.
-- Early recognition and prompt isolation of suspected cases remain critical to reduce further transmission.
Laboratory
-- Laboratory testing of suspected cases should be conducted as part of the outbreak response.
-- Laboratory investigations may include molecular detection, serology, and sequencing to support case confirmation and better understand the outbreak.
-- Recommendations on laboratory approaches will continue to evolve as new evidence becomes available.
Case management
-- Early identification, prompt isolation, and clinical evaluation of suspected cases are essential.
-- When HPS is suspected, patients should be promptly referred for close monitoring and supportive care, including admission to emergency or intensive care settings when needed.
-- Clinical management is primarily supportive and may include antipyretics, careful fluid management, hemodynamic monitoring, respiratory support, and escalation to advanced interventions for severe cases.
-- Mechanical ventilation, vasopressors, extracorporeal membrane oxygenation[4] (ECMO), or dialysis may be required for severe disease.
-- Antibiotics are not routinely indicated for confirmed hantavirus infection, but may be used empirically if bacterial infection cannot be ruled out or is suspected.
-- Currently, there is no approved specific antiviral treatment for HPS.
Infection Prevention and Control
-- Suspected or confirmed cases should be isolated in a single, well-ventilated room.
-- Standard precautions* should be applied at all times for all patients, including hand hygiene, environmental cleaning, and appropriate waste management, outlined in the interim guidance published on 8 May
-- Transmission-based precautions should be implemented in addition to standard precautions. Health and care workers should use appropriate personal protective equipment, including respirators, eye protection, gowns, and gloves.
-- Suspected or confirmed cases should be isolated in a single, well-ventilated room.
-- Transmission-based precautions should be implemented in addition to standard precautions.
-- Hand hygiene should be performed before and after the use of PPE.
-- Waste from suspected or confirmed cases should be managed as infectious waste.
-- Airborne precautions should be applied during aerosol-generating procedures.
-- The duration of standard and transmission-based precautions should be determined on a case-by-case basis.
Risk Communication and Community Engagement (RCCE)
-- Communication strategies should prioritize transparent, timely, and culturally appropriate information to affected individuals and the general public.
-- Risk Communication and Community Engagement (RCCE) efforts should provide clear, consistent, and actionable information, including explanations of the public health measures being implemented.
-- Messaging should address public concerns regarding transmissibility, severity, and international travel, and clarify recommended actions for different population groups.
-- Public health awareness should focus on early detection, timely healthcare seeking, and reducing exposure risks, including occupational and environmental exposures.
-- RCCE activities should be integrated throughout all phases of the response and align with broader public health measures.
-- Environmental management strategies, including rodent control, should be included as part of prevention efforts.
-- Based on the current information available on this event, WHO advises against the application of any travel or trade restrictions beyond the restriction of movement of identified high-risk contacts.
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{*} Standard precautions refer to a set of practices that are applied to the care of patients, regardless of the state of infection (suspicion or confirmation), in any place where health services are provided. These practices aim to protect both healthcare professionals and patients and include hand hygiene, use of personal protective equipment, respiratory hygiene and cough etiquette, safe handling of sharps materials, safe injection practices, use of sterile instruments and equipment and cleaning of hospital environments and the environment. Adapted from “Standard precautions for the prevention and control of infections: aide-memoire”- WHO, 2022. Available at https://www.who.int/publications/i/item/WHO-UHL-IHS-IPC-2022.1
Further information
-- World Health Organization. Management of contacts of Andes virus (ANDV) cases from the MV Hondius cruise ship. https://www.who.int/publications/m/item/management-of-contacts-of-andes-virus-(andv)-cases-fromthe-mv-hondius-cruise-ship
-- World Health Organization. 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
-- World Health Organization. Hantavirus fact sheet. https://www.who.int/news-room/fact-sheets/detail/hantavirus
-- World Health Organization.WHO’s response to hantavirus cases linked to a cruise ship. https://www.who.int/news/item/07-05-2026-who-s-response-to-hantavirus-cases-linked-to-a-cruise-ship
-- World Health Organization. Handbook for management of public health events on board ships. https://www.who.int/publications/i/item/9789241549462
-- World Health Organization. Guide to Ship Sanitation, 3rd edition https://www.who.int/publications/i/item/9789241546690
-- World Health Organization. Handbook for management of public health events in air transport, https://www.who.int/publications/i/item/9789241510165
-- World Health Organization. Guide to hygiene and sanitation in aviation, 3rd edition, https://www.who.int/publications/i/item/9789241547772
-- Preliminary analysis of Orthohantavirus andesense virus sequences from a cruise-ship related cluster, May 2026. https://virological.org/t/preliminary-analysis-of-orthohantavirus-andesense-virus-sequences-from-a-cruise-ship-related-cluster-may-2026/1029
-- World Health Organization. Standard precautions for the prevention and control of infections: aide-memoire. https://www.who.int/publications/i/item/WHO-UHL-IHS-IPC-2022.1
-- World Health Organization. Transmission-based precautions for the prevention and control of infections: aide-memoire. https://www.who.int/publications/i/item/WHO-UHL-IHS-IPC-2022.2
-- World Health Organization. Hantavirus outbreak toolbox. https://www.who.int/emergencies/outbreak-toolkit/disease-outbreak-toolboxes/hantavirus-outbreak-toolbox
-- World Health Organization (8 May 2026). Disease Outbreak News. Hantavirus cluster linked to cruise ship travel, Multi-country. Available at: https://www.who.int/emergencies/disease-outbreak-news/item/2026-DON600
-- World Health Organization (4 May 2026). Disease Outbreak News. Hantavirus cluster linked to cruise ship travel- Multi-country. Available at: https://www.who.int/emergencies/disease-outbreak-news/item/2026-DON599
-- World Health Organization. A decision framework for effective, equitable and context-specific public health and social measures during public health emergencies: decision navigator: https://iris.who.int/server/api/core/bitstreams/ceaf4aa7-00c8-4681-9c35-965e231a3706/content
-- Pan American Health Organization / World Health Organization. Infection prevention and control of hantavirus infection, including Andes virus disease. Interim regional guidance for suspected or confirmed cases. https://iris.paho.org/items/bc5a7b5a-5a0a-4407-829e-663c762ad615
-- Pan American Health Organization / World Health Organization. Clinical management of hantavirus infection, including Andes virus disease: Interim regional guidance for suspected or confirmed cases. https://iris.paho.org/items/0fa0dcb1-4395-467d-a431-5408b4eff337
-- Pan American Health Organization / World Health Organization. PAHO supports the international response to hantavirus pulmonary syndrome cases linked to a cruise ship in the Atlantic. https://www.paho.org/en/news/7-5-2026-paho-supports-international-response-hantavirus-pulmonary-syndrome-cases-linked
-- Epidemiological Alert Hantavirus Pulmonary Syndrome (HPS). https://www.paho.org/en/documents/epidemiological-alert-hantavirus-pulmonary-syndrome-americas-region-19-december-2025
-- Hantavirus in the Americas: Guidelines for diagnosis, treatment, prevention and control. Available at: https://iris.paho.org/handle/10665.2/40176
-- Hantavirus Prevention, CDC: https://www.cdc.gov/hantavirus/prevention/?CDC_AAref_Val=https://www.cdc.gov/hantavirus/hps/prevention.html
-- Martínez Valeria, Paola N, et al. (2020). “Super-Spreaders” and Person-to-Person Transmission of Andes Virus in Argentina. New England Journal of Medicine. 383. 2230-2241. 10.1056/NEJMoa2009040.
-- US CDC. How to Clean Up After Rodents: https://www.cdc.gov/healthy-pets/rodent-control/clean-up.html
-- Hantavirus, Washington State Department of Heath, https://doh.wa.gov/sites/default/files/2025-08/420-056-Guideline-Hantavirus.pdf
-- Hantavirus Infection, MDS Manual, professional version: https://www.msdmanuals.com/professional/infectious-diseases/arboviruses-arenaviridae-and-filoviridae/hantavirus-infection
-- Hantavirus pulmonary syndrome, https://www.mayoclinic.org/diseases-conditions/hantavirus-pulmonary-syndrome/symptoms-causes/syc-20351838
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[1] Preliminary analysis of Orthohantavirus andesense virus sequences from a cruise-ship related cluster, May 2026. https://virological.org/t/preliminary-analysis-of-orthohantavirus-andesense-virus-sequences-from-a-cruise-ship-related-cluster-may-2026/1029
[2] “Super-Spreaders” and Person-to-Person Transmission of Andes Virus in Argentina | New England Journal of Medicine. https://www.nejm.org/doi/full/10.1056/NEJMoa2009040
[3] Padula PJ, Edelstein A, Miguel SD, López NM, Rossi CM, Rabinovich RD. Hantavirus pulmonary syndrome outbreak in Argentina: molecular evidence for person-to-person transmission of Andes virus. Virology. 1998 Feb 15;241(2):323-30. doi: 10.1006/viro.1997.8976. PMID: 9499807. https://pubmed.ncbi.nlm.nih.gov/9499807/
[4] Dietl CA, Wernly JA, Pett SB, et al. Extracorporeal membrane oxygenation support improves survival of patients with severe Hantavirus cardiopulmonary syndrome. The Journal of Thoracic and Cardiovascular Surgery. 2008;135(3):579-584. doi:10.1016/j.jtcvs.2007.11.020.
Citable reference: World Health Organization (28 May 2026). Disease Outbreak News. Hantavirus outbreak linked to cruise ship travel, Multi-locations. Available at: https://www.who.int/emergencies/disease-outbreak-news/item/2026-DON604
Source:
Link: https://www.who.int/emergencies/disease-outbreak-news/item/2026-DON604
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