Regional Update, Influenza and Other Respiratory Viruses. Epidemiological Week 28 (19 July 2024)

[WEEKLY SUMMARY]. Regional Situation: During the last four epidemiological weeks (EW), low levels of Influenza-Like Illness (ILI) activity have been reported across the Americas. However, there has been epidemic activity in the Southern Cone and an increase in activity in the Caribbean and Central America subregions. This rise is associated with the circulation of influenza in the Southern Cone, Central America, and the Caribbean, as well as SARS-CoV-2 in the Caribbean and Central America. Additionally, there has been a decrease in Severe Acute Respiratory Infection (SARI) activity, with epidemic levels in the Southern Cone, Andean subregion, and Central America, related to positive cases of influenza and RSV. Regarding respiratory virus circulation, 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. Influenza epidemic activity has been declining, especially in the Southern Cone, while showing an increasing trend in Central America. Respiratory Syncytial Virus (RSV) activity has remained low, except in the Andean subregion and the Southern Cone, where epidemic levels and an increasing trend have been observed. North America: ILI, SARI, and hospitalizations associated with respiratory viruses have remained low during the last four EW, although there has been an increase in the proportion of positive SARS-CoV-2 cases. Influenza activity has remained below the epidemic threshold in all countries. The predominant influenza viruses during this period have been type A(H3N2), followed by A(H1N1)pdm09, and B/Victoria. RSV activity has remained low. SARS-CoV-2 activity has shown an increase, with some countries experiencing moderate to high levels compared to previous waves. By country: • Canada: SARS-CoV-2 activity has increased to moderate levels compared to previous waves. Influenza activity remains below the epidemic threshold, and RSV activity has remained low. • Mexico: ILI and SARI cases remain stable at epidemic levels, with an increase in positive cases attributable to SARS-CoV-2, which is on the rise. Influenza activity remains below the epidemic threshold. • United States: Hospitalization rates for influenza, RSV, and SARS-CoV-2 remain low, although there has been a slight increase in positive SARS-CoV-2 cases. This activity has increased in recent EWs, 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, associated with a higher proportion of positive SARS-CoV-2 and influenza cases. Although 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. During this period, the predominant viruses have been type A(H3N2), with less circulation of influenza A(H1N1)pdm09. RSV activity has remained low. SARS-CoV-2 activity remains stable at elevated levels. By country: Influenza activity has been observed in the last four EWs in the Dominican Republic, Jamaica, and Guyana. SARS-CoV-2 activity has been observed in Belize, the Dominican Republic, Jamaica, Saint Lucia, Suriname, Barbados, Guyana, the Cayman Islands, and Saint Vincent and the Grenadines. • Dominican Republic: SARI activity has increased to epidemic levels, coinciding with an epidemic of influenza. • Jamaica: There has been an increase in SARI cases above the epidemic threshold, coinciding with a marked increase in SARS-CoV-2 and influenza activity. • Guyana: ILI and SARI cases have increased, with positive cases attributable to both SARS-CoV-2 and influenza. Central America: ILI and SARI activity remain fluctuating at epidemic levels, with most positive cases attributable to influenza, followed by SARS-CoV-2 and RSV. Influenza activity has increased during the last four EWs, reaching epidemic levels in several countries in the subregion. During this period, the predominant influenza viruses have been type A(H3N2), with less circulation of A(H1N1)pdm09. RSV and SARS-CoV-2 activity, although increasing, remain low. By country: • El Salvador: Influenza circulation has again reached high levels, and SARS-CoV-2 is on the rise, although at low levels compared to previous waves. • Guatemala: ILI activity has increased above the epidemic threshold and SARI activity above the moderate threshold. Most positive ILI cases are attributed to influenza, whose circulation has declined to below the epidemic threshold, and SARI cases to RSV, whose activity is on the rise. • Honduras: In the last four EW, SARI activity has fluctuated at epidemic levels, mainly associated with positive influenza cases, currently at moderate levels, and SARS-CoV-2, which is on the rise. • Nicaragua: Influenza activity has increased above the high threshold, while RSV and SARS-CoV-2 circulation remains low. • Panama: ILI and SARI cases have increased in the last four EW, coinciding with influenza activity that, after reaching moderate levels, has declined to epidemic levels in the last EW. There has also been an increase in the proportion of positive SARS-CoV-2 and RSV cases, whose activity is increasing. Andean Region: ILI and SARI activity has remained stable at epidemic levels during the last four EW, associated with an increase in the proportion of positive RSV and influenza cases. Influenza activity has continued to decline in the last four EW. During this period, the predominant influenza viruses have been type A(H3N2), with concurrent circulation of A(H1N1)pdm09 and type B/Victoria. RSV activity has remained stable at moderate levels. SARS-CoV-2 activity, although at low levels, has shown a marked increase. By country: • Bolivia: SARI cases are decreasing, with levels below the epidemic threshold. The few positive cases are attributable to influenza, whose activity has decreased to below the epidemic threshold. • Colombia: SARI activity, after reaching epidemic levels in recent weeks, has decreased below this threshold, with most positive cases attributable to RSV, whose activity is at intermediate levels compared to previous seasons. To a lesser extent, positive cases are attributed to influenza, whose activity is below the epidemic threshold. Acute Respiratory Infection (ARI) cases have reached extraordinary levels. • Ecuador: SARI and pneumonia activity has increased in recent EW, reaching moderate levels. Positive SARI cases are mainly attributable to influenza, whose activity is at epidemic levels. To a lesser extent, they are attributed to RSV, which is declining, and SARS-CoV-2, which is increasing. • Peru: SARI cases have increased, especially associated with positive RSV cases, whose activity is on the rise, and to a lesser extent influenza, whose activity is below the epidemic threshold. There has also been increasing SARS-CoV-2 activity, although it remains low. • Venezuela: Influenza activity has decreased to below the epidemic threshold. Brazil and the Southern Cone: After the increase observed in previous weeks, ILI and SARI activity has decreased in the last four EW, with most positive cases attributable to RSV and to a lesser extent influenza. Influenza activity is at epidemic levels in some countries, while in others it has declined 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 has remained on the rise, although it is still at lower levels compared to peaks reached in previous seasons. SARS-CoV-2 activity has remained low. By country: • Argentina: ILI activity, after reaching high levels, has decreased to epidemic levels, while SARI activity, after reaching epidemic levels, has decreased below this threshold. Influenza activity has reached extraordinary levels, showing a decrease in the last four EW to moderate levels. At the same time, an increase in the positivity rate of RSV has been observed, reaching values similar to the peaks observed in previous seasons. • Brazil: ILI and SARI activity has decreased to 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 currently decreasing, at epidemic levels. Most positive cases during the last four EW are attributable to RSV, whose activity is increasing, although positivity levels are below the peaks observed in previous seasons. Influenza activity, after reaching extraordinary levels, has decreased to below the epidemic threshold. • Paraguay: SARI activity has shown a rebound to moderate levels, related to positive cases of RSV and, to a lesser extent, SARS-CoV-2, whose activity is on the rise. ILI activity, after reaching epidemic levels, has decreased below this threshold, with most cases associated with influenza, whose activity is decreasing but still at epidemic levels. • Uruguay: SARI activity, after reaching high levels, has decreased to moderate levels where it remains stable, with most positive cases attributable to RSV and to a lesser extent influenza. The latter, after reaching moderate levels, has decreased to below the epidemic threshold. RSV activity has shown an increase, reaching levels similar to the peaks observed in previous seasons.