Origin, contact tracing scope, why case counts keep changing, and what to watch next as the multi-country Andes virus cluster enters its second month.
The 2026 MV Hondius cluster is the first hantavirus outbreak to attract sustained global attention since the 2018-19 Epuyén person-to-person event. It is also the first hantavirus event to involve a cruise ship, multi-country contact tracing, and a coordinated WHO IHR response. Here is what we know — and what we do not.
The MV Hondius is a 107-passenger Dutch-flagged polar expedition vessel operated by Oceanwide Expeditions out of Vlissingen, Netherlands. The ship runs Antarctic and sub-Antarctic itineraries during the southern summer. Its 1 April 2026 sailing carried 147 passengers and crew of 23 nationalities — the breadth of the contact tracing operation derives directly from this passenger mix.
Investigators believe the index couple — both Dutch nationals — were infected before boarding the ship. They had completed a bird-watching trip through Argentina, Chile and Uruguay in March 2026, including visits near a landfill outside Ushuaia where the long-tailed pygmy rice rat (the Andes virus reservoir) is known to be present.
This pre-cruise exposure window matches the Andes virus incubation period of 1-6 weeks. The husband fell ill on 6 April, five days into the cruise; the wife on approximately 22-23 April, three weeks after they would have left Ushuaia. Argentine authorities have launched a rodent-trapping program to confirm the exposure site, but the investigation is ongoing.
Andes virus has documented person-to-person transmission, which is why the cluster is being treated with seriousness. The challenge is that any of the 147 people on the ship could have been infected by the index couple, and any of those could have transmitted onward. When the ship called at Saint Helena on 24 April, approximately 30 passengers disembarked — and one of them, the symptomatic wife of the index case, then flew via KLM through Johannesburg.
That single flight has triggered contact tracing for hundreds of secondary contacts across multiple countries. So far, eight French nationals have been identified on that flight; one has shown mild symptoms. The U.K., Netherlands, Germany, Switzerland, France, South Africa and the United States are all running their own tracing operations.
Suspected case counts have moved up and down over the past week. This is normal for an active outbreak — testing takes time, exposure histories get clarified, and some suspected cases turn out to be unrelated respiratory illness. The 8 May ruling-out of two Singaporean residents (negative tests, released from isolation) is an example of the system working as intended.
As of 10 May 2026 the working figure is 9 cases (6 confirmed, 3 suspected) and 3 deaths. We update these numbers as new information comes in.
Three reasons:
The remaining suspected cases will resolve to either confirmed or ruled-out within the next 7-14 days. If a tertiary case appears — meaning someone infected by a Hondius secondary contact who never set foot on the ship — that would be a meaningful escalation. So far there is no evidence of that.
The other thing worth watching is whether any genomic sequencing reveals an unusual Andes variant. To date, statements from PAHO and Argentina indicate the virus is consistent with circulating strains, but full sequencing data has not been released publicly.