Regional Update, Influenza and Other Respiratory Viruses. Epidemiological Week 53 (9 January 2026)

Regional Situation: Influenza activity in the Americas continues an upward trend, mainly driven by increased activity in the Northern Hemisphere, with a regional positivity of 30.1%. Influenza A(H3N2) continues to predominate among subtyped samples in all regions, except in the Andean subregion. RSV circulation remains at low levels (<1%), while SARS-CoV-2 positivity continues to decline, reaching 5.1%. In North America, influenza circulation continues to increase, reaching a positivity of 30.7%. RSV activity remains low, with a slight increase to 2.2%, while SARS-CoV-2 positivity decreased to 5.2%. In the Caribbean, influenza activity remained stable over the past four epidemiological weeks (EWs), following a period of intense activity, reaching a positivity of 33%. SARS-CoV-2 circulation remained low and stable, while RSV activity remained elevated at 12.3%. In Central America, influenza activity continues to increase, reaching a positivity of 22.6%. SARS-CoV-2 circulation remained low and stable, while RSV activity remained elevated at 9.1%. In the Andean subregion, influenza activity increased over the past two EWs, reaching a positivity of 11.8%, while RSV and SARS-CoV-2 circulation decreased over the past three EWs, with positivities around 4%. In Brazil and the Southern Cone, influenza activity decreased compared with previous EWs, with a positivity below 10%. RSV circulation remains at interseasonal levels (<1%), while SARS-CoV-2 activity continued to increase over recent EWs, reaching 12.3%. Circulation of other respiratory viruses (ORVs) has continued to decline since early October, with a regional positivity of 2.0%. Rhinovirus and parainfluenza remain the most frequently detected ORVs.