The Ministry of Health of the Nation released the latest Epidemiological Bulletin, reporting an increase in leptospirosis cases and the circulation of respiratory viruses, especially influenza A(H3N2).
Between epidemiological week 1 and 15 of this year, 109 notifications of leptospirosis were recorded, of which 45 were confirmed and 64 probable. The current incidence rate is 0.23 cases per 100,000 inhabitants, representing a 28% increase compared to last year.
Geographical distribution of leptospirosis
- Central Region: concentrates 86 cases (Santa Fe 39, Buenos Aires 28, Entre Ríos 15).
- NEA: 15 cases (Misiones 8, Corrientes 5).
- South: 3 cases (La Pampa and Río Negro).
- Cuyo: 1 case (San Luis).
In canine leptospirosis, 32 confirmed cases were reported, 27% less than in 2025. The Central region concentrates 81% of the total, with Buenos Aires leading.
Characteristics of human cases
- 78% are males.
- Median age: 38 years.
- Higher disease burden: between 20 and 49 years (67% of the total).
The rodents are the main reservoir, although cases are also recorded in companion and production animals. Dogs function as sentinel animals, as their infection indicates the presence of the bacteria in the environment.
The main risk of contagion in Argentina is associated with prolonged contact with water and mud during floods, in addition to urban deficiencies in sanitation and waste collection.
Increase in respiratory viruses
The circulation of influenza A(H3N2) drives the increase in respiratory cases. Positivity rose from 33.3% in week 18 to 42.2%.
In genomic characterization, ANLIS Malbrán detected 11 new cases of the J.2.4.1 (K) subclade, reaching a total of 194 detections, with wide distribution in 23 jurisdictions, especially in the NOA and Central regions.
Arboviruses and other viruses
- Chikungunya: 258 new cases, with a progressive decline after the peak in week 16 (430 cases). The cumulative total for the 2025-2026 season is 2,387 cases, 96% concentrated in the NOA.
- Hantavirus: a new case linked to the MV Hondius cruise was reported, raising the outbreak to 9 confirmed and 2 probable. The total for the season is 106 cases, with higher incidence in Salta.
- Dengue: 67 confirmed cases since the start of the season, 60% with no travel history. The rest are people with trips to Brazil, Paraguay, Mexico, Colombia, and other countries.
The epidemiological bulletin reflects a complex scenario: an increase in leptospirosis in the Central and NEA regions, an increase in influenza A(H3N2) with national circulation, and sustained presence of arboviruses such as chikungunya and dengue.
Coordination between the Ministry of Health, ANLIS Malbrán, SENASA, and the Undersecretariat of Environment is key to facing these challenges and strengthening epidemiological surveillance in Argentina.
