Epidemic hazard

On 2 May 2026, WHO and ECDC were formally notified by the national authorities of the initially involved countries about a cluster of severe acute respiratory illness with 2 deaths and 1 critically ill passenger aboard a cruise ship departed from South Argentina on April 1, with 149 passengers and crew from 23 countries. On May 6, 2026, WHO confirmed that the responsible agent is the Andes (ANDV), a hantavirus variant endemic in some areas of South America causing a severe respiratory disease with a high fatality rate and that, unlike most hantaviruses, has occasionally shown limited human-to-human transmission among close and prolonged contacts. The outbreak is being managed by international and national authorities through a coordinated international response, including in-depth epidemiological investigations, case isolation and clinical management, lab testing and international contact tracing and monitoring. Detailed updates are regularly provided (cf. sources). As of the latest information available (May 14, 2026) 11 cases have been reported (8 confirmed, two probable, and one inconclusive) including 3 deaths (CFR 38%). The outbreak is transitioning from an active maritime crisis to a multi-country public health monitoring phase as all passengers and most crew members have been disembarked and repatriated for localized quarantine, while a smaller crew is currently operating the ship to bring it to the Netherlands with a medical team ensuring monitoring and clinical support onboard. All confirmed and probable cases are limited, as of May 14, to cruise ship passengers and crew. An RFI has been sent to EpiCore members asking support in the collection of publicly available information to monitor the event in real time. The network was requested to provide professional comments based on personal experience or reliable documentation of similar outbreaks, to support the assessment of the risk of additional cases, and define necessary interventions to reduce this risk. Several members responded with their professional opinion. Below is a summary of their contributions: Relevant direct sources and repositories of online reliable information were shared. It was noted that the time lapse between the death of the first case and the onset of the following three cases (one of which was a close contact and another shared bathrooms with the first two) over a short duration, pointed strongly since the beginning towards common exposure (to case 1) and a superspreading event. Therefore human-to-human spread has been correctly considered however shared environmental exposure during earlier travels remains a plausible explanation at least for a part of the cluster and needs to be further investigated. Deeper genetic analysis will help the definition of the exact nature of the virus and the mapping of how it has moved through cases. The importance of timely results of the genetic investigations being made available since the beginning by the involved authorities (cf. sources) was noted as valuable for understanding the exact nature of the virus and mapping it through the cases. To explain the dynamic of this cluster of cases it was also suggested that, while literature tends to state that ANDV human-to-human transmission requires close and extended contact, it cannot be excluded that the virus can actually pass more easily than we think from person to person and that the reason this is rarely described is that there are not enough documented clusters. The rarity may reflect the limited spillover exposure from the reservoir and not necessarily the fact that the virus is not so capable of spreading once someone is infected. It was also suggested the likelihood of identifying cases outside the ship in relation to the fact that several passengers disembarked before the outbreak was reported. This aspect may have played a key role in terms of risk of further spread as data from past outbreaks (cf. sources) show that it can take more than one month from exposure for symptoms to appear. It was noted that the response activities so far implemented by national and international authorities in close collaboration have been appropriate and may limit this possibility of further spread in case they are maintained for all the time needed (i.e. 42-day monitoring period). Regarding the management of patients it has been emphasized that the resulting sustained respiratory distress requires immediate intervention. Due to the disease's sudden onset and rapid progression, early diagnosis and accurate supportive treatment is critical to prevent secondary bacterial infections that can further complicate the clinical outcomes. The RFI has been contributed by relevant information and technical comments in support to the assessment of the current risk in relation to this event. This summary may be updated in case of additional relevant contributions received by the network that may change the current assessment. OFFICIAL SOURCES (examples) - https://www.who.int/emergencies/disease-outbreak-news (WHO regular updates) - https://www.ecdc.europa.eu/en/infectious-disease-topics/hantavirus-infection/surveillance-and-updates/andes-hantavirus-outbreak (ECDC regular updates) - https://www.cdc.gov/hantavirus/situation-summary/index.html (US CDC regular updates) - https://www.who.int/emergencies/disease-outbreak-news/item/2026-DON601 (WHO - May 13, 2026) - https://www.who.int/emergencies/disease-outbreak-news/item/2026-DON600#:~:text=PCR%20testing%20confirmed%20hantavirus%20infection,virus%20was%20confirmed%20through%20sequencing. (WHO - May 8, 2026) - https://www.ecdc.europa.eu/sites/default/files/documents/TAB-hantavirus-06052026.pdf (ECDC risk assessment - May 6, 2026) - https://www.ecdc.europa.eu/en/news-events/ecdc-publishes-guidance-management-passengers-linked-andes-hantavirus-outbreak-cruise (ECDC guidance for the management of passengers - May 9, 2026) - https://www.ecdc.europa.eu/en/publications-data/outbreak-andes-virus-2026-recommendations-self-quarantine (ECDC recommendations for self-quarantine – May 13, 2026) - https://www.canada.ca/en/public-health/services/emergency-preparedness-response/rapid-risk-assessments-public-health-professionals/rapid-risk-assessment-hantavirus-andes-virus-outbreak-international-cruise-ship.html (Gov of Canada Rapid Risk Assessment – May 8, 2026) OTHER RELEVANT SOURCES (examples) - Complete sequence of ANDV virus, Switzerland: https://virological.org/t/complete-sequence-of-orthohantavirus-andesense-virus-swiss-resident-2026/1023 - CIDRAP report (May 12, 2026): https://www.cidrap.umn.edu/misc-emerging-topics/hantavirus-outbreak-grows-11-cases-9-confirmed - CIDRAP report (May 13, 2026): https://www.cidrap.umn.edu/misc-emerging-topics/cdc-risk-general-public-hantavirus-low - Martínez VP et al. "Super-Spreaders" and Person-to-Person Transmission of Andes Virus in Argentina. N Engl J Med. 2020 Dec 3;383(23):2230-2241. doi: 10.1056/NEJMoa2009040. PMID: 33264545 INFORMATION REPOSITORIES (examples) - BEACON: https://beaconbio.org/en/event/?eventid=5fd6edf4-ca36-4761-8dc8-cb8632a43977& - GENOMIC EPI: https://genomicepi.com/outbreaks/hantavirus-hondius/ - GITHUB Hantavirus Outbreak Data Repository 2026: https://github.com/kraemer-lab/Hondius_hantavirus_h2026 - TRANSMISSIBLE: https://openandv.fieldepi.eu/