Hantavirus activity in May 2026 is at its highest global alert level since the 2018–2019 Chilean cluster. The primary driver is the MV Hondius expedition cruise cluster, a novel and unexpected transmission scenario that has prompted rapid international response. This article provides a situation report current as of early May 2026.
The MV Hondius Cluster: What We Know
The MV Hondius cluster is the first documented hantavirus cluster associated with an Antarctic expedition cruise vessel. As of the most recent case count, 8 cases have been confirmed across 8 nationalities, with 3 deaths — a case fatality rate of approximately 37.5%, consistent with the known range for Andes virus HPS.
Timeline of key events:
- Mid-April 2026: First case identified in the Netherlands, returning passenger from MV Hondius
- Late April 2026: WHO Disease Outbreak Notice issued; passenger contact tracing initiated across 12 countries
- Early May 2026: Cases confirmed in Germany, UK, US, Chile, Argentina, Australia, and Canada; WHO preliminary assessment notes “limited but not conclusive” evidence of person-to-person transmission
- May 10–11, 2026: Canada confirms 8th case (Vancouver, BC); ECDC upgrades risk to European travellers to “moderate”
Epidemiology: The viral strain in all cases is confirmed as Andes virus (ANDV), the dominant South American variant. Genomic sequencing to determine whether all cases share a common source (the ship) or include secondary transmission events is ongoing. Results are expected within weeks and will be decisive for the person-to-person transmission question.
Exposure hypothesis: Current leading hypothesis is rodent stowaway in provisions loaded in Ushuaia, Argentina. Shore landing exposure at sub-Antarctic islands is an alternative under active investigation.
Argentina: Seasonal Context
Argentina accounts for the majority of global hantavirus burden, with the Patagonian Andean zone being the world’s highest-prevalence endemic region for Andes virus. The 2025–2026 Southern Hemisphere season runs from November through April.
Season-to-date 2025–2026: Argentina has recorded approximately 104 confirmed cases for the 2025–2026 season, of which the majority are in Río Negro, Neuquén, and Chubut provinces. This figure is broadly consistent with recent years: Argentina typically records 80–150 cases per year. Case fatality rates in well-managed clinical settings in Argentina have improved over the past decade as early recognition has improved.
Current status: The Argentine hantavirus season is at its tail end — the autumn months see declining rodent activity as temperatures drop. However, the Hondius cluster has triggered additional surveillance in the Ushuaia port region and adjacent Tierra del Fuego.
Global Case Counts by Country (Active Reporting)
| Country | 2025–2026 Season | Historical Context |
|---|---|---|
| Argentina | ~104 | 80–150/year typical |
| USA | ~25 | 20–35/year typical |
| Chile | ~18 | 10–25/year typical |
| Brazil | ~8 | 3–15/year typical |
| Panama | ~3 | 1–5/year typical |
| Canada | 1 | Rare; prior to 2026, fewer than 5 historical |
| Hondius cluster (international) | 8 | No prior comparable event |
Note: Hondius cluster cases are separately tracked as an outbreak event associated with vessel exposure rather than regional endemic exposure.
WHO Assessment
The World Health Organization has issued three advisories in connection with the Hondius cluster:
- Disease Outbreak Notice (DON-599): Initial alert, describing the cluster and initiating multi-country contact tracing
- Updated DON (DON-601): Expanded case count, early genomic sequencing results, preliminary P2P transmission assessment
- Advisory for Antarctic cruise operators: Recommending rodent risk assessment for vessels loading provisions in endemic South American ports
WHO has not recommended any travel restriction or port closure, and the overall public health risk assessment for general travellers remains low. The cluster is unusual but containable given the identified exposure pathway.
ECDC Assessment
The European Centre for Disease Prevention and Control issued a Rapid Risk Assessment on May 8, upgrading the risk to European travellers on Antarctic-route cruises from “very low” to “moderate.” The specific concern is:
- Multiple European passengers affected (Netherlands, Germany, UK confirmed among the 8 cases)
- Antarctic expedition cruising is a popular activity among European adventure travellers
- Awareness of hantavirus risk in this context is minimal in European medical systems
ECDC recommendations include briefing travel medicine clinics in ECDC member states and developing specific pre-departure information for Antarctic cruise passengers.
Key Uncertainties to Resolve
Several questions will shape the next phase of this outbreak:
Person-to-person transmission: The most consequential open question. If ANDV transmitted person-to-person aboard the ship, it will significantly change the risk calculus for any enclosed environment with a confirmed ANDV case — not just ships. Full genomic sequencing results are the key evidence. See our dedicated article on Andes virus P2P transmission.
Source of vessel contamination: If rodents were present aboard MV Hondius, that finding will have immediate implications for the entire Antarctic cruise industry. A negative finding shifts focus to shore landing exposure pathways.
Sub-Antarctic wildlife reservoir: Whether South Georgia mice or other sub-Antarctic rodent populations carry hantaviruses is essentially uncharacterised. If they do, it would represent a newly identified reservoir with implications for Antarctic research stations as well as tourism.
What to Monitor
Over the coming weeks, the following developments will be the most diagnostically important:
- Genomic sequencing results from WHO/PAHO collaboration — expected within 3–4 weeks
- MV Hondius inspection findings from Argentine port authority — will determine whether rodent evidence was found aboard
- Additional cases — the contact tracing pool is approximately 200 former passengers and crew; additional cases would extend the outbreak
- Argentine port regulations — draft regulations expected from Spain and potentially IAATO
For continuous tracking, the outbreak map is updated as new cases and events are confirmed. For full timeline of the Hondius cluster, see MV Hondius Outbreak: Complete Timeline.
Sources
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