Hantavirus disease is an emerging zoonosis caused by viruses of the genus Orthohantavirus. Transmission to humans occurs mainly through the inhalation of aerosols contaminated with viral particles from the faeces, urine or saliva of wild rodents.
Key data:
- 108 confirmed cases during the 2025–2026 epidemiological season, from EW 27 of 2025 to EW 22 of 2026.
- 36 deaths and a case fatality rate of 33.3%.
- National incidence of 0.23 cases per 100,000 inhabitants, the highest among the seasons compared since 2019–2020.
- The season remained above the outbreak threshold for almost the entire period.
- The Central region reported 56 cases; the Northwest, 39; the South, 12; and the Northeast, one.
- Buenos Aires accounted for 44 cases and 18 deaths.
- Salta reported 32 cases and the highest incidence in the country: 2.11 cases per 100,000 inhabitants.
- A total of 81% of cases occurred in men, and 70% were concentrated among people aged 20–49 years.
There were 47 confirmed cases during 2026 up to EW 22, compared with a historical median of 29. The situation was considered “above expected levels” both for the annual cumulative total and for the previous four weeks.
In the Americas, the most common clinical presentation is hantavirus cardiopulmonary syndrome. It usually begins abruptly with fever, general malaise and gastrointestinal symptoms, followed by respiratory distress and hypotension. In Argentina, the case fatality rate ranged from 10% to 32% during 2019–2024.
Person-to-person transmission is possible, particularly with Andes virus, and close contact with a confirmed case is therefore considered a suspected exposure. People with fever of unknown origin, with or without myalgia, chills, weakness, headache or abdominal pain, should also be investigated when they have been exposed during the previous six weeks to rodents or places inhabited by their reservoirs.
Risk areas and seasonality
- Northwest: Salta, Jujuy and Tucumán.
- Northeast: Misiones, Formosa and Chaco.
- Central region: Buenos Aires, Santa Fe and Entre Ríos.
- South: Neuquén, Río Negro and Chubut.
Although cases can occur throughout the year, the highest incidence is observed between October and May. The expansion of urban settlements into rural areas, habitat destruction, interaction with wild environments and climatic effects may contribute to cases occurring outside historically endemic areas.
Temporal evolution
Between EW 27 of 2018 and EW 22 of 2026, 651 confirmed cases were recorded. The 2018–2019 season included the person-to-person transmission outbreak in Epuyén, Chubut, and accumulated 126 cases.
A total of 56% of cases during the period occurred between October and January. During the current season, November accounted for 16 cases, December for 21 and January for 17. These figures were higher than those recorded during the same months in previous seasons, excluding the Epuyén outbreak.
In the Northwest, the seasonal increase usually begins earlier, with the highest numbers of cases occurring in October and November. In the Central and Southern regions, the peaks are usually recorded in December and January.
Situation by region
Central region: The Central region reported 56 cases and remained above the outbreak threshold throughout the period. The main increase occurred between EW 45 of 2025 and EW 5 of 2026. This was followed by a plateau and a slight increase between weeks 13 and 22. Cases were recorded in Buenos Aires, Entre Ríos and Santa Fe.
Argentine Northwest: The Northwest reported 39 cases. The cumulative curve increased continuously from late 2025 and remained within the alert zone, although it did not exceed the outbreak threshold. Cases were concentrated exclusively in Salta and Jujuy.
Southern region: The Southern region recorded 12 cases in Chubut, Neuquén and Río Negro. The cumulative curve exceeded the outbreak threshold from EW 35 of 2025, although the bulletin warns that the stepwise pattern should be interpreted in view of the low absolute number of cases.
Argentine Northeast: The Northeast recorded a single case during the season, corresponding to Formosa, with a regional incidence of 0.02 cases per 100,000 inhabitants.
Case outside the historically endemic area
A case was reported in a resident of Río Colorado, Río Negro, a locality situated outside the historically endemic areas. Four potential exposure sites were investigated in Río Colorado and La Adela, La Pampa.
Trapping showed a low abundance of rodents. No species recognised as reservoirs of pathogenic hantaviruses were captured, and the animals studied tested negative by serology. Nevertheless, there are historical reports of reservoir rodents in the area, and periodic environmental monitoring was therefore recommended.
Family cluster in Chubut
An intrafamilial cluster involving three people living in the same household, with sequential symptom onset, was recorded in Cerro Centinela, Chubut.
During the environmental investigation, wild rodents recognised as reservoirs were captured, and one specimen found around the home tested positive for hantavirus. Analysis of the human samples identified Andes virus, with 99.99% genomic similarity among the three cases.
The pattern was considered compatible with a chain of person-to-person transmission. However, because a positive rodent was identified, a shared zoonotic exposure could not be ruled out. At the time the bulletin was published, genomic sequencing of the virus detected in the rodent was still pending.
