Regional Update, Influenza and Other Respiratory Viruses. Epidemiological Week 30 (2 August 2024)

[WEEKLY SUMMARY]. Regional Situation: Over the last four epidemiological weeks (EWs), epidemic levels of Influenza-Like Illness (ILI) have been reported in the Southern Cone, along with increased activity in North America, the Caribbean, and Central America. This increase is associated with 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 observed in the Southern Cone, the Andean subregion, and Central America, driven by positive cases of influenza and RSV. At the regional level, SARS-CoV-2 activity has remained at moderate levels compared to previous epidemic waves, although there has been an uptick linked to increased circulation in North America, the Caribbean, Central America, and the Andean subregion. Similarly, while influenza activity has remained at epidemic levels in the Southern Cone and Central America, it is now on the decline. RSV activity has risen to epidemic levels in Central America, the Andean subregion, and the Southern Cone, with a growing trend observed. North America: Cases of ILI, SARI, and hospitalizations associated with 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 strains have been A(H3N2), followed by A(H1N1)pdm09 and B/Victoria. RSV activity has remained low. However, SARS-CoV-2 activity has increased, reaching moderate to high levels in some countries compared to previous waves. By Country: • Canada: SARS-CoV-2 activity has increased, reaching levels close to those seen in previous peaks. Influenza activity remains below the epidemic threshold, while RSV activity has stayed low. • Mexico: Cases of ILI and SARI have increased to moderate and epidemic levels, respectively, driven by a rise in positive SARS-CoV-2 cases. Influenza and RSV activity remain low. • United States: The SARS-CoV-2 hospitalization rate per 100,000 inhabitants has risen in recent weeks, reaching levels similar to those during 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 influenza cases. While SARI cases have remained low, there has been an increase in the proportion of positive SARS-CoV-2 and influenza cases. Influenza activity has remained at intermediate levels during the last four EWs, with A(H3N2) being predominant, followed by A(H1N1)pdm09. RSV activity has stayed low, while SARS-CoV-2 activity continues to be stable at elevated levels. By Country: In the last four EWs, influenza activity has been reported in Belize, 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. RSV activity has been observed in Suriname, Guyana, and Saint Vincent and the Grenadines. • Dominican Republic: An increase in SARI activity has been detected, reaching epidemic levels, coinciding with epidemic influenza activity and SARS-CoV-2 circulation. • Saint Lucia: An increase in SARI activity has been observed, reaching epidemic levels, associated with SARS-CoV-2 circulation. • Guyana: An increase in ILI and SARI cases has been reported, with positive cases attributed to SARS-CoV-2, influenza, and to a lesser extent, RSV. 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 activity. After peaking at epidemic levels in several countries in the subregion, influenza activity has shown a decline over the last four EWs. During this period, A(H3N2) has been the predominant influenza virus. RSV activity has reached levels similar to the peaks recorded in previous seasons. Although SARS-CoV-2 activity is increasing, it remains below the levels seen in previous waves. By Country: • Costa Rica: Following an increase in ILI and SARI cases in previous weeks, a declining trend has been observed over the last four EWs, with most positive cases attributed to SARS-CoV-2 and, to a lesser extent, influenza. • El Salvador: After reaching moderate levels, influenza circulation has declined over the last four EWs. SARS-CoV-2 activity remains low compared to previous waves. • Guatemala: An increase in ILI activity to moderate levels has been observed, with most positive cases attributed to influenza and SARS-CoV-2. SARI activity remains constant at epidemic levels; however, there has been a marked increase in the proportion of positive RSV cases. • Honduras: Over the past four EWs, SARI activity has fluctuated between epidemic and moderate levels, primarily associated with positive influenza cases, which are now in decline but still at epidemic levels, and to a lesser extent, SARS-CoV-2. • Nicaragua: After peaking above the high threshold in influenza circulation during the last four EWs, activity is now declining to epidemic levels, while RSV and SARS-CoV-2 circulation remains low. • Panama: ILI and SARI cases have increased over the last 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 during the last four EWs in most countries. Additionally, there has been an increase in the proportion of positive RSV and SARS-CoV-2 cases. Influenza activity has continued to decline during this period. A(H3N2) has been the predominant influenza virus. RSV activity has remained stable at moderate levels, while SARS-CoV-2 activity has shown a sharp increase to moderate 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, 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 attributed to influenza, which is at epidemic levels, and to a lesser extent, 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 attributed 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 A(H3N2) and A(H1N1)pdm09. RSV activity has remained stable, reaching a peak, although it is still below the maximum levels observed 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. At the same time, an increase in RSV positivity has been observed, reaching values similar to the peaks seen 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: Following the decline observed in previous weeks, a slight uptick in ILI and SARI cases has been reported, reaching moderate and epidemic levels, respectively. Most positive cases during the last four EWs are attributed to RSV, which continues to rise, although positivity levels remain below the peaks seen in previous seasons. Influenza activity, after reaching extraordinary levels, has decreased 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 SARS-CoV-2 and influenza. • Uruguay: SARI activity, after reaching high levels, has decreased to moderate levels and 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.