Patagonian index cluster: eight Andes-virus cases linked to Río Negro lodge

What happened On 18 February 2026, the Argentine Ministerio de Salud declared a provincial outbreak in Río Negro with eight confirmed Andes-virus cases linked to a single tourism lodge in Bariloche. Whole-genome sequencing established that the cluster represents a single introduction. The first probable household-acquired secondary case was identified by 25 February in a contact with no documented rodent-exposure history.

What changed since last update The Bariloche cluster remains the recognised origin for the 2026 outbreak. Subsequent cases (MV Hondius, March; Norway, April) are connected by either documented travel/visitation or, in Norway's case, a separate suspected research-rodent exposure pathway under active investigation. No new lodge-linked cases have been reported since the initial 8.

Official source summary - Lodge cases: 8 confirmed (RT-PCR + serology) - Probable household secondary case: 1 (identified 25 Feb) - Deaths within the lodge cluster: 0 reported as of WHO DON #600 - Genomic origin: single introduction, Patagonian Andes-virus lineage - Provincial response: lodge closed; rodent-control and serosurvey programmes ongoing

Market impact - Will WHO declare a PHEIC for hantavirus by Dec 31, 2026? — the lodge cluster anchors the outbreak narrative. A confirmed second European autochthonous case would shift the trajectory; a quiet summer in Patagonia keeps it bearish. - Will MV Hondius–attributed deaths exceed 10 by July 1, 2026? — indirectly relevant: the lodge cluster confirms an active local reservoir at the time the Hondius docked at Puerto Madryn.

Open questions 1. Was the household secondary case truly person-to-person transmission, or environmental? 2. What is the seroprevalence in the lodge's surrounding rodent population? 3. Does the WGS lineage match the MV Hondius isolate?

Timeline - ~05 Feb 2026 — First lodge guest develops HPS-consistent symptoms. - 18 Feb 2026 — Provincial outbreak declared (8 cases). - 25 Feb 2026 — First probable household-acquired secondary case identified. - 01 Mar 2026 — INEI-ANLIS Malbrán publishes WGS bulletin: single introduction. - 08 May 2026 — Lodge cluster numbers unchanged; included in WHO DON #600 as the recognised origin.

Sources See sources block below. Background: 2026 outbreak timeline, Andes virus deep dive.