Regional Update, Influenza and Other Respiratory Viruses. Epidemiological Week 29 (26 July 2024)

[WEEKLY SUMMARY]. Regional Situation: During the last four epidemiological weeks (EWs), epidemic levels of Influenza-Like Illness (ILI) have been observed in the Southern Cone, alongside increased activity in the subregions of North America, the Caribbean, and Central America. This uptick is linked to the circulation of influenza in the Southern Cone, Central America, and the Caribbean, as well as SARS-CoV-2 in North America, the Caribbean, and Central America. Additionally, epidemic levels of Severe Acute Respiratory Infection (SARI) have been reported in the Southern Cone, the Andean subregion, and Central America, largely driven by positive cases of influenza and RSV. At the regional level, SARS-CoV-2 activity has remained low compared to previous epidemic waves, although there has been an increase associated with circulation in North America, the Caribbean, Central America, and the Andean subregion. Similarly, influenza has reached epidemic levels in the Southern Cone and Central America. RSV activity has also risen to epidemic levels in Central America, the Andean subregion, and the Southern Cone, where a growing trend has been observed. North America: Cases of ILI, SARI, and hospitalizations linked to respiratory viruses have increased, with a notable rise in the proportion of positive SARS-CoV-2 cases. Influenza activity has remained below the epidemic threshold across all countries. During this period, the predominant influenza viruses have been type A(H3N2), followed by A(H1N1)pdm09 and B/Victoria. RSV activity has stayed low. However, SARS-CoV-2 activity has increased, reaching medium to high levels in some countries compared to previous waves. By Country: • Canada: SARS-CoV-2 activity has risen to medium levels compared to previous waves. Influenza activity remains below the epidemic threshold, while RSV activity has stayed low. • Mexico: ILI cases have increased, driven by a rise in positive SARS-CoV-2 cases. SARI cases have remained stable, although the proportion of positive SARS-CoV-2 cases has increased. Influenza and RSV activity remains low. • United States: The SARS-CoV-2 hospitalization rate per 100,000 inhabitants has risen in recent weeks, reaching levels similar to the peaks of 2023 and 2024. Both influenza and RSV activity remain low. Caribbean: In the last four EWs, ILI cases have increased, accompanied by a higher proportion of positive SARS-CoV-2 and influenza cases. While SARI cases have remained low, an uptick in positive SARS-CoV-2 and influenza cases has been noted. Influenza activity has stayed at intermediate levels during the last four EWs, with a predominance of A(H3N2) and, to a lesser extent, A(H1N1)pdm09. RSV activity has remained low, while SARS-CoV-2 activity continues to be elevated. By Country: In the last four EWs, influenza activity has been reported in the Dominican Republic, Jamaica, the Cayman Islands, and Guyana. SARS-CoV-2 activity has been detected in Belize, the Dominican Republic, Jamaica, Saint Lucia, Suriname, Barbados, Guyana, the Cayman Islands, and Saint Vincent and the Grenadines. • Dominican Republic: A rise in SARI activity has been observed, reaching epidemic levels, coinciding with epidemic influenza activity and SARS-CoV-2 circulation. • Guyana: Increases in ILI and SARI cases have been noted, with positive cases attributable to both SARS-CoV-2 and influenza. Central America: There has been an increase in ILI and SARI activity, with most positive cases attributed to influenza, followed by SARS-CoV-2 and RSV, both of which have shown rising proportions. Influenza activity, after peaking at epidemic levels in several countries of the subregion, has shown a decline in the last EW. During the last four EWs, the predominant influenza viruses have been type A(H3N2) with less circulation of A(H1N1)pdm09. RSV activity has reached levels similar to the peaks recorded in previous seasons. Although SARS-CoV-2 activity is increasing, it remains low compared to previous waves. By Country: • El Salvador: Influenza circulation, after reaching moderate levels, has declined over the last four EWs. SARS-CoV-2 activity continues to rise, though it remains low compared to previous waves. • Guatemala: An increase in ILI and SARI activity above the epidemic threshold has been observed. Most positive ILI cases are attributed to influenza, which has now dropped below the epidemic threshold, while SARI cases are mainly due to RSV and, to a lesser extent, SARS-CoV-2, which is on the rise. • Honduras: Over the past four EWs, SARI activity has fluctuated at epidemic levels, mainly driven by positive influenza cases, which are currently at epidemic levels, and rising SARS-CoV-2 activity. • Nicaragua: In the last four EWs, influenza activity peaked above the high threshold and is now in decline, while RSV and SARS-CoV-2 circulation remains low. • Panama: ILI and SARI cases have increased over the past four EWs, with a rise in the proportion of positive SARS-CoV-2 and RSV cases. Influenza activity has dropped below the epidemic threshold. Andean Region: ILI and SARI activity has remained at epidemic levels over the last four EWs in most countries. Additionally, an increase in the proportion of positive RSV and SARS-CoV-2 cases has been observed. Influenza activity has continued to decline during this period. The predominant influenza viruses have been type A(H3N2), with concurrent circulation of A(H1N1)pdm09 and B/Victoria. RSV activity has remained stable at moderate levels, while SARS-CoV-2 activity has shown a sharp increase to medium levels compared to previous waves. By Country: • Bolivia: SARI cases are on the decline, now below the epidemic threshold. Influenza activity has also decreased to levels below this threshold. • Colombia: SARI activity, after reaching epidemic levels in recent weeks, has declined below this threshold. Most positive cases are attributed to RSV, which is at intermediate levels compared to previous seasons, and to a lesser extent to SARSCoV- 2, which is on the rise, with intermediate circulation levels compared to previous waves. ARI (Acute Respiratory Infection) cases remain at extraordinary levels. • Ecuador: SARI and pneumonia activity has remained around the moderate threshold in the last four EWs. Most positive SARI cases are attributable to influenza, which is at epidemic levels, and to a lesser extent to RSV and SARS-CoV-2, both of which are increasing. • Peru: An increase in SARI cases has been observed, reaching extraordinary levels, particularly associated with positive RSV cases, which are on the rise, and to a lesser extent influenza, which remains below the epidemic threshold. Additionally, growing SARS-CoV-2 activity has been recorded, although it remains at low levels. • Venezuela: A decline in influenza activity has been observed, now below the epidemic threshold. Brazil and the Southern Cone: Following the increases observed in previous weeks, ILI and SARI activity has declined over the last four EWs, with most positive cases attributable to RSV and, to a lesser extent, influenza. Influenza activity remains at epidemic levels in some countries, while in others, it has dropped below this threshold, showing a decreasing trend. During this period, the predominant influenza viruses have been type A(H3N2) and, to a lesser extent, A(H1N1)pdm09. RSV activity continues to rise, although it remains below the peaks reached in previous seasons. SARS-CoV-2 activity has remained low. By Country: • Argentina: ILI activity, after reaching high levels, has declined to epidemic levels, while SARI activity, after reaching epidemic levels, has fallen below this threshold. Influenza activity, after peaking at high levels, has decreased to epidemic levels in the last EW. Concurrently, an increase in RSV positivity has been observed, reaching values similar to the peaks observed in previous seasons. • Brazil: ILI and SARI activity has decreased below the epidemic threshold, with the highest proportion of positive cases attributed to RSV and influenza. • Chile: ILI and SARI cases, after reaching extraordinary levels this season, are now declining, currently at epidemic levels. Most positive cases over the last four EWs are attributable to RSV, which continues to rise, although positivity levels remain below the peaks seen in previous seasons. Influenza activity, after reaching extraordinary levels, has dropped below the epidemic threshold. • Paraguay: SARI activity has rebounded to moderate levels, related to positive RSV cases and, to a lesser extent, SARS-CoV- 2, whose activity is increasing. ILI activity, after reaching epidemic levels, has decreased below this threshold, with most cases associated with influenza, which remains at epidemic levels but is declining. • Uruguay: SARI activity, after reaching high levels, has decreased to moderate levels, where it remains stable, with most positive cases attributed to RSV and, to a lesser extent, influenza. The latter, after reaching moderate levels, has dropped below the epidemic threshold. RSV activity has risen, reaching levels similar to the peaks observed in previous seasons.