Argentina is the global epicentre of Andes virus activity. Every year, between May and October — the Southern Hemisphere autumn and winter — cases rise as the Oligoryzomys longicaudatus rodent population peaks and people spend more time in enclosed rural spaces. The 2026 season, already complicated by the MV Hondius cluster, is shaping up to be one of the most closely watched in the country’s surveillance history.
Argentina’s Historical Hantavirus Burden
Since Argentina began systematic hantavirus surveillance in the mid-1990s following the first documented Andes virus cases, the country has recorded over 1,200 cases with a cumulative case fatality rate approaching 35%. The provinces most consistently affected are Neuquén, Río Negro, and Chubut in Patagonia, along with Salta and Jujuy in the northwest where a different hantavirus strain — Oran virus — predominates.
The virus does not spread evenly. Patagonia’s semi-arid steppe provides ideal habitat for O. longicaudatus, whose population fluctuates dramatically with mast seeding events (years of exceptional seed production by southern beech trees, Nothofagus species) that drive rodent population explosions. A high-mast year two to three years prior is one of the strongest predictors of a high-case hantavirus year in Patagonia.
The 2026 Season: Data as of May 11
PAHO’s weekly bulletin as of May 11, 2026, records 104 confirmed hantavirus cases in Argentina for the current season (January 1 – May 11, 2026), with 34 deaths — a case fatality rate of 32.7%, consistent with the historical average.
This places 2026 on track to be the highest-case year since 2018 when La Niña-driven conditions produced an exceptional rodent bloom. The current season is running approximately 20% above the five-year average for the same epidemiological weeks.
Provincial Distribution (2026, weeks 1–19)
| Province | Cases | Deaths | CFR |
|---|---|---|---|
| Neuquén | 31 | 10 | 32% |
| Río Negro | 24 | 8 | 33% |
| Chubut | 19 | 6 | 32% |
| Salta | 14 | 5 | 36% |
| Buenos Aires | 8 | 2 | 25% |
| Other | 8 | 3 | 38% |
Source: PAHO Weekly Hantavirus Bulletin, Week 19, 2026
The relatively lower CFR in Buenos Aires province reflects faster access to intensive care. The higher CFR in “Other” provinces reflects delayed clinical presentation in remote areas.
What Is Driving the 2026 Spike?
Climate conditions: A La Niña event in 2023–2024 produced above-average rainfall in Patagonia, triggering exceptional seed production by southern beeches and other vegetation in 2024. Rodent populations exploded in 2025 and remain elevated entering 2026, creating a persistent high-exposure environment.
Rural activity: Post-pandemic recovery of rural tourism, farming, and forestry in Patagonia has brought more people into contact with rodent habitats. Authorities note that a significant proportion of 2026 cases involve urban residents visiting rural cabins — the classic high-risk scenario.
The Hondius crew connection: One confirmed 2026 case is the crew member linked to MV Hondius, reported on May 10. While this case is technically part of the cruise ship cluster, it is also counted in Argentina’s national total, reflecting the geographic origin of that patient’s exposure.
Surveillance and Response Infrastructure
Argentina’s National Health Ministry runs a dedicated hantavirus surveillance programme through its provincial health networks, with mandatory case reporting, contact tracing, and environmental sampling. The response protocol activates automatically when a confirmed case is identified, deploying epidemiologists to investigate the likely rodent exposure site.
Rodent population monitoring stations in Neuquén and Río Negro provide monthly data on O. longicaudatus abundance, informing early warning alerts. When indices exceed threshold values, the ministry issues public advisories targeting rural workers, tourists, and communities in high-risk zones.
PAHO supports Argentina’s surveillance through technical assistance, laboratory networking, and the regional hantavirus information platform that aggregates data from Argentina, Chile, Brazil, Bolivia and Paraguay.
What Argentina’s Experience Teaches Global Health
Several lessons from Argentina are relevant to global hantavirus management:
Seasonal prediction works: Argentina has shown that combining rodent population data with meteorological modelling can produce reliable seasonal risk forecasts 4–8 weeks in advance, allowing targeted public health messaging before case rises occur.
Early clinical suspicion saves lives: The most significant predictor of survival is time from symptom onset to intensive care. In Argentina, case fatality in patients who reach ICU in the early cardiopulmonary phase is substantially lower than in those presenting late.
Community education matters: The provinces with the most sustained public education campaigns — particularly Neuquén — show better case-to-hospitalisation ratios, suggesting that informed patients seek care faster.
What to Watch for the Rest of 2026
The hantavirus season in Patagonia typically peaks in July–August, the deepest Southern Hemisphere winter months, when people seal their homes and rural structures tightly and rodents move indoors seeking warmth. Current rodent population indices suggest the peak may arrive slightly earlier than usual in 2026.
If MV Hondius genomic data confirms rodent exposure during an Antarctic shore landing as the index event, it would have implications for how biosafety is managed on Antarctic voyages globally — a niche but important area where Argentina’s hantavirus expertise will be directly relevant.
Track Argentina’s live case count and compare with other countries on the global outbreak map. For information on symptoms and when to seek care, read the hantavirus symptoms guide.
Sources
- PAHO Hantavirus Bulletin, Week 19, 2026
- Argentina National Health Ministry Surveillance Reports
- CDC Argentina Hantavirus Information
- ECDC Hantavirus Situation Overview
Explore HantavirusMap