WHO revised DON 600 on 9 May, upgrading the ship-level risk for the MV Hondius cluster from LOW to MODERATE and confirming that all six laboratory-tested cases were Andes virus by PCR and full genome sequencing.1 The revision supersedes the original DON 599 assessment, which logged 7 cases, 3 deaths, and applied standard hantavirus droplet precautions rather than the Andes-specific airborne isolation tier. The Swiss case , confirmed days after DON 599 was published, is the event that forced the upgrade: the Andes strain identification changed both the transmission model and the infection-control calculus.
At the point of revision, the WHO case count stood at 8 cases (6 confirmed, 2 probable) and 3 deaths, producing a 38% case-fatality rate. That CFR is consistent with the baseline for Andes hantavirus in laboratory-confirmed cases, which historically runs 30-40%. The six reporting countries at the time of revision were the Netherlands, South Africa, Switzerland, Germany, the United Kingdom, and Spain. A MODERATE ship-level risk assessment indicates that transmission from the MV Hondius environment to passengers is considered plausible, though person-to-person secondary transmission ashore had not been confirmed.
PAHO's December 2025 Epidemiological Alert had already placed Southern Cone health authorities on notice about rising hantavirus case-fatality figures before the voyage , and the pre-voyage birding expedition traversed Oligoryzomys longicaudatus habitat in Chile, Uruguay, and Argentina, according to WHO's Maria Van Kerkhove, establishing the most plausible rodent-exposure window.2 The vessel completed disembarkation at Tenerife on 11 May, closing the primary exposure environment. The MODERATE designation remains in force while contact tracing and 45-day incubation monitoring continue across all six countries.
