Regional Update, Influenza and Other Respiratory Viruses. Epidemiological Week 39 (4 October 2024)

Abstract

[WEEKLY SUMMARY]. Regional Situation: Influenza-Like Illness (ILI) and Severe Acute Respiratory Infection (SARI) activity has shown a general downward trend in recent weeks. In North America and the Caribbean, most cases have been associated with SARS-CoV-2, followed by influenza. In Central America, the Andean region, and the Southern Cone, cases have declined, with the majority of positives linked to RSV, SARS-CoV-2, and influenza. SARS-CoV-2 activity remains high and increasing in North America, Brazil, and the Southern Cone. Influenza has shown a generalized decrease, although fluctuations persist in certain Caribbean and Andean countries. RSV activity has begun to decline in the Andean subregion and the Southern Cone after reaching epidemic levels in previous weeks, while it remains high in some Central American countries and is increasing in some Caribbean countries. North America: Cases of ILI, SARI, and hospitalizations associated with respiratory viruses have continued to decline over the past four EW, following an increase in previous weeks. The majority of positive cases are attributable to SARS-CoV-2, though this proportion is also decreasing. Influenza activity has remained below the epidemic threshold across all countries. During this period, the predominant influenza viruses have been A(H3N2), followed by A(H1N1)pdm09 and B/Victoria. RSV activity has remained low. In contrast, SARS-CoV-2 activity has remained at levels similar to the peaks observed in the previous 2023- 2024 wave. By country: • In Canada, SARS-CoV-2 activity remains on the rise, reaching levels close to the peaks recorded in previous waves. Influenza activity remains below the epidemic threshold, while RSV activity is low. • In Mexico, after rising to moderate levels in previous weeks, ILI and SARI cases have shown a marked decline over the last four EW to epidemic levels. Most positive cases are attributable to SARS-CoV-2, which is declining. Both influenza and RSV activity remain low. • In the United States, the SARS-CoV-2-associated hospitalization rate per 100,000 inhabitants has shown a decrease over the last four weeks. SARS-CoV-2 positivity levels, after reaching values similar to peaks observed i2023 and 2024, have shown a downward trend over the last four EW. Influenza and RSV activity continue to be low.

[RESUMEN SEMANAL]. Situación regional: la actividad de Enfermedad Tipo Influenza (ETI) e Infección Respiratoria Aguda Grave (IRAG) ha mostrado una tendencia general a la baja en las últimas semanas. En América del Norte y el Caribe, la mayor parte de los casos ha estado asociada a SARS-CoV-2 y en menor medida a influenza. En América Central, la región Andina y el Cono Sur, los casos han disminuido, con la mayoría de los positivos vinculados a VRS, SARS-CoV-2 e influenza. La actividad de SARS-CoV-2 continúa siendo elevada y ascendente en Norteamérica, y Brasil y el Cono Sur. La influenza ha mostrado una disminución generalizada, aunque sigue presentando fluctuaciones en ciertos países del Caribe y la subregión Andina. La actividad del Virus Respiratorio Sincitial (VRS) ha comenzado a descender en la subregión Andina y el Cono Sur, tras alcanzar niveles epidémicos en semanas previas, y se mantiene alta en algunos países de América Central y en ascenso en algunos países del Caribe.