Hantavirus Global Situational Briefing — May 21, 2026

ECDC cluster status (as of May 20): 11 total cases — 9 confirmed, 2 probable — 3 deaths. No new cases or deaths since the May 17 update. Rotterdam decontamination of MV Hondius enters its fourth and potentially final day. Argentina opens a 150-trap rodent survey in Ushuaia's forests. A US passenger formally challenges her CDC federal quarantine order.

Cluster Scorecard: ECDC Revises Down to 11

The European Centre for Disease Prevention and Control issued its May 20 situational update with a notable revision: the cluster now stands at 11 total cases — 9 laboratory-confirmed, 2 probable, 3 deaths — down from the 12-case figure cited on May 18. 1

ECDC explicitly confirmed that no new cases or deaths have been reported since its previous update, indicating a stable period following the cluster's rapid growth in early May. The Spain second provisional positive — a mildly symptomatic evacuee at Hospital Gómez Ulla — does not appear in the official confirmed or probable tally as of May 20, suggesting Spanish authorities are treating it as pending further confirmation.

The case fatality proportion among confirmed cases remains approximately 25% (3 deaths out of 12 total counted at peak), consistent with clinical data from historical Andes virus outbreaks in Argentina and Chile.

Rotterdam: Decontamination Day 4, RIVM Inspection Imminent

EWS Group's decontamination of the MV Hondius entered its fourth day on May 21 at Rotterdam's Calandsteiger 7 berth. Oceanwide Expeditions had estimated the process would take three to four days, placing completion on May 21–22, subject to RIVM's post-decontamination inspection and sampling results. 2

Quarantine status as of May 21 (unchanged from prior day):

25 crew + 2 RIVM medical staff remain aboard
38 Filipino crew: PCR-negative; in precautionary 42-day quarantine at Rotterdam port facilities; Dutch Maritime Workers Union (DMW) confirmed all negative
2 Dutch crew: home quarantine
12 Radboudumc (Nijmegen) healthcare workers: six-week precautionary quarantine running through late June, following protocol breach during patient treatment on May 7

Oceanwide Expeditions confirmed that sailings scheduled for May 29 and June 5 are canceled. Full operations are targeted to resume June 13, departing from Longyearbyen, Svalbard — contingent on RIVM clearance. 2

Pasteur Sequencing: No Novel Variants, 97% ANDV Similarity Confirmed

France's Institut Pasteur released full genomic results this week confirming that the Andes virus detected in the French patient is 97% similar to known Andes virus strains already circulating in South America, including rodent-linked samples. 3

"The analyzed virus corresponds to the viruses already known and monitored in South America. At this stage, no element suggests the emergence of a form of the virus that could be more transmissible or more dangerous." — French Health Minister Stéphanie Rist, via X

Jean-Claude Manuguerra (Pasteur, Environment and Infectious Risk unit) noted that the remaining ~3% variation reflects normal viral diversity and does not appear to affect viral characteristics. The viruses sampled across ship-linked patients were identical to one another — consistent with a single zoonotic introduction, as posited by the NEJM correspondence published this week.

The NEJM correspondence analyzed the first 10 confirmed cases, noting high genomic similarity (at most 1 SNP divergence across patients) and placing the likely initial zoonotic spillover in Argentina before the April 1 departure from Ushuaia. 4

Argentine scientists wearing masks and gloves carry wooden box traps through forest undergrowth in Ushuaia, searching for the hantavirus reservoir source

Argentine investigators trap rodents in the forests surrounding Ushuaia on May 19, 2026, in the first systematic effort to identify the zoonotic reservoir that likely seeded the MV Hondius outbreak. (Photo: AP via kdhnews.com)

Argentina Launches Rodent Survey in Ushuaia Forests

On May 19–20, Argentine investigators set 150 box traps overnight in the forests surrounding Ushuaia — the world's southernmost city and the departure point of the MV Hondius on April 1. The goal is to identify whether Andes virus is circulating in local rodent populations in an area not historically considered an ANDV hotspot. 5

Researchers collected dead rodents in black plastic bags and transported them to a field laboratory for blood sample extraction. Protective equipment included blue nitrile gloves and medical masks. Results have not yet been publicly released.

Identifying the zoonotic reservoir source is critical: the NEJM analysis concluded that the most probable scenario is a single animal-to-human spillover in Argentina prior to departure, with subsequent limited person-to-person transmission on board. However, whether that spillover occurred in Ushuaia's urban-adjacent forests, at an Argentinian pre-departure excursion site, or in transit along the South Atlantic route remains unresolved.

Patient Conditions: France ECMO, Spain Pending

France: The 65-year-old female passenger continues on ECMO support at Hôpital Bichat AP-HP in Paris. No updated status change has been publicly confirmed as of May 21 morning. She remains in critical condition — the sole case among the 11 still in acute hospital care at this stage.

Spain: The 70-year-old first patient at Hospital Gómez Ulla was approaching discharge as of May 20. A second evacuee at Gómez Ulla remains classified as provisionally positive pending confirmatory testing: asymptomatic with low-grade fever and mild respiratory symptoms; the other 13 evacuees tested negative. This case is not yet counted in the official ECDC cluster total.

Canada: The Yukon resident (70s) confirmed by PHAC remains stable in Victoria, BC; travel partner continues to test negative.

Switzerland: Patient 7 (the Swiss case) remains hospitalized.

US: Federal Quarantine Challenged, Nebraska Monitoring Continues

CDC federal quarantine orders — the first issued for the MV Hondius outbreak under 42 CFR Parts 70 and 71 and signed by acting CDC Director Jay Bhattacharya — cover two passengers at the Nebraska Quarantine Unit (NQU) through May 31. 6

Passenger Angela Perryman, a former emergency management professional with eight years of Iraq fieldwork, has formally signaled intent to challenge the order. Speaking to Inside Medicine, she confirmed she tested negative on both PCR and antibody (IgM and IgG) blood tests, arguing the order lacks consistency given her current non-infectious status. She expressed a desire to complete monitoring under home quarantine. 7

All 18 passengers at the NQU have been asked to remain through May 31 (the 21-day mark of monitoring). The broader US monitoring cohort stands at approximately 41 people across 12 states (AZ, CA, GA, KS, MD, MN, NE, NJ, TX, UT, VA, WA); monitoring window closes June 22. Zero confirmed US Andes virus cases remain linked to the Hondius outbreak. The Illinois Winnebago County case (previously under CDC investigation) returned negative and was formally closed May 19.

Domestic HPS: Two Independent US Sin Nombre Cases

Two unrelated hantavirus cases underscore that endemic transmission continues in parallel with the Hondius cluster:

Douglas County, Colorado (announced May 16): An adult resident died from Sin Nombre hantavirus following local rodent exposure. The Colorado Department of Public Health explicitly confirmed no link to the cruise ship outbreak. 8
Chelan County, Washington: The Chelan-Douglas Health District confirmed a Sin Nombre hantavirus case in a county resident. No link to MV Hondius. 9

Sin Nombre HPS carries an approximately 38% case fatality rate when diagnosed in the United States, per CDC. Both cases are consistent with the seasonal spring-summer rodent-activity pattern in western states.

WHO Holds First «Hantavirus in Focus» Webinar

On May 20, WHO convened «Hantavirus in Focus I: what we know and what it means» — the organization's first formal knowledge-sharing forum for the outbreak. The webinar covered outbreak epidemiology, global and country perspectives, with Spain and the United Kingdom presenting national response experiences. 10

WHO stated that as of May 13, 11 cases and 3 deaths were on record, and described its response as operating under IHR (2005) coordination — emphasizing information sharing, contact tracing support, and risk communication. The event signals an intent to systematize knowledge from the outbreak for future expedition-travel and biosafety guidance. A follow-up session (Focus II) was noted in closing remarks.

Situation Summary Table

Dimension	Status (May 21, 2026)
ECDC official cluster (as of May 20)	11 cases: 9 confirmed, 2 probable; 3 deaths
Spain second provisional case	Pending confirmation; not in ECDC total
France ECMO patient	Critical; no change
Spain first patient	Approaching discharge
Canada Yukon case	Stable
Rotterdam decontamination	Day 4; RIVM inspection imminent
Oceanwide resume date	June 13 (Longyearbyen)
US Andes monitoring	~41 persons / 12 states; 0 confirmed US cases
Nebraska federal quarantine	2 passengers under order through May 31
WHO status	Global risk: Low

Watchlist for May 22

RIVM post-decontamination inspection result for MV Hondius — clearance (or not) to proceed toward June 13 restart
Spain second provisional case confirmatory PCR from Gómez Ulla
France ECMO patient daily status update
Argentina rodent survey results from Ushuaia trapping campaign
Argentina BEN SE19 weekly epidemiological bulletin (expected)
ECDC CDTR Week 21 (expected May 22) — first to formally cover May 18+ decontamination period
WHO DON-602 — still pending publication on the WHO Disease Outbreak News feed