Regional Update, Influenza and Other Respiratory Viruses. Epidemiological Week 52 (2 January 2026)

Regional Situation: IInfluenza activity in the Americas continues to trend upward, with a positivity rate of 15.68% for the last week. Influenza A(H3N2) predominated among subtype-identified samples in all regions except the Andean subregion, where influenza A(H1N1)pdm09 predominated. RSV circulation remains at low levels, with an upward trend and a positivity rate of 1.9% in the last epidemiological week (EW), while SARS-CoV-2 shows a downward trend, with a positivity rate of 6.3%.  In North America (data through EW 51), influenza positivity reached 18.8%, showing a sustained and pronounced increase over the last four weeks. RSV activity remains low with an upward trend, while SARS-CoV-2 positivity remained close to 3.16%, lower than in previous EWs. In the Caribbean, influenza circulation reached a positivity rate of 26.8%. RSV activity remained high, with a positivity rate of 12%, while SARS-CoV-2 remained at low levels, with a positivity rate below 1%. In Central America, influenza activity showed a sustained increase during the last weeks, reaching a positivity rate of 16.6%. SARS-CoV-2 remained at low and stable levels, while RSV circulation shows a downward trend, at 8.9%. In the Andean subregion, influenza activity reached a positivity rate of 10.7% and is trending upward; SARS-CoV-2 and RSV circulation remains low and is declining compared to the previous two weeks, reaching positivity rates of 3.6% and 5.7%, respectively. In Brazil and the Southern Cone, influenza activity for this week shows a downward trend with a positivity rate of 11.2%. RSV circulation remains at low seasonal levels and a positivity rate of <1%, while SARS-CoV-2 activity increased and reached a positivity rate of 10%. The circulation of other respiratory viruses (ORV) increased to 9.5% at the regional level, with the subregion of Brazil and the Southern Cone showing the largest increase.