A Shift in the Winter Health Landscape
According to the latest National Epidemiological Bulletin (BEN) for week 30, the circulation of respiratory viruses has changed its main protagonist in Argentina.
Respiratory Syncytial Virus (RSV)—a common virus that typically causes mild cold-like symptoms but can lead to severe lower respiratory tract infections in infants—has surpassed influenza as the primary cause of hospitalization for severe acute respiratory infections. While flu cases have steadily declined since their peak in weeks 21 and 22, RSV continues to rise, predominantly affecting the pediatric population.
+65,000
Bronchiolitis cases reported up to epidemiological week 28 in 2026.
2,267
Hospitalizations with RSV detection reported so far this year.
What is RSV and Who is at Risk?
RSV is the leading cause of bronchiolitis and lower respiratory infections in early childhood. Official data indicates that in the last four weeks analyzed, 200 positive RSV cases were detected in hospitalized patients, compared to 76 for influenza. The most vulnerable group is children under 2 years of age, with an even greater impact on babies between 6 and 11 months old.
Dr. Néstor Vain, a pediatrician and neonatologist, warned that most children who develop severe illness were born healthy and full-term, without underlying risk factors. This means all babies are at risk, as it is impossible to predict which infants will develop severe symptoms.
The Challenge of Maternal Prevention
Although Argentina added maternal vaccination against RSV to its National Schedule in 2024 (administered between weeks 32 and 36 of pregnancy to transfer antibodies to the baby), many infants reach their first viral circulation season without sufficient protection. This happens due to births outside the vaccination window or the natural waning of protection received during pregnancy over the months.
Provincial Innovation: The Case of Córdoba
To bridge this protection gap, the province of Córdoba (one of Argentina's most populated regions) became the first jurisdiction to implement an integrated strategy, incorporating nearly 10,000 doses of nirsevimab. This is a long-acting monoclonal antibody that protects healthy newborns and those with risk conditions born since January 1, 2026. Other provinces, such as Santa Fe and San Juan, are also advancing in the adoption of this tool.
Dr. Analía De Cristófano, head of the Pediatric Infectology Section at the Italian Hospital of Buenos Aires, celebrated having effective tools today, but stressed that the challenge is ensuring all infants go through their first season of virus circulation protected.
Other Viruses and the Arbovirus Outlook
The BEN also reported on the simultaneous circulation of viruses. There were 10 co-detections, mostly of influenza and RSV. Meanwhile, pneumonia cases have been decreasing since week 22, and SARS-CoV-2 remains at low levels.
Regarding arboviruses (viruses transmitted by mosquitoes), the outlook is favorable. Dengue remains in a low-risk scenario nationwide, with 70 confirmed cases throughout the 2025-2026 season. Chikungunya fever recorded 3,618 cases this season, concentrated at 97% in the NOA region (the Argentine Northwest, comprising provinces like Salta, Tucumán, and Jujuy).