Regional Update, Influenza and Other Respiratory Viruses. Epidemiological Week 24 (21 June 2024)

[WEEKLY SUMMARY]. During the last four epidemiological weeks (EWs), 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 activity is associated with the circulation of influenza in the Southern Cone and Central America and SARS-CoV-2 in the Caribbean. Additionally, moderate levels of Severe Acute Respiratory Infection (SARI) have been observed, particularly in the Southern Cone, followed by the Andean subregion. In both cases the activity is related to positive cases of influenza and RSV. Regarding the circulation of respiratory viruses, SARS-CoV-2 activity has remained at low levels compared to previous epidemic waves, although showing an increase associated with circulation in North America and the Caribbean. Additionally, there has been rising epidemic-level influenza activity, marked by circulation in Central America, the Southern Cone, and some Caribbean countries. RSV activity has remained low except in the Andean region, where moderate levels have been observed. North America: ILI cases and hospitalizations associated with respiratory viruses have continued to decline over the past four EWs, remaining at low levels. Influenza activity has also continued to decrease, staying below the epidemic threshold. During this period, the predominant influenza viruses have been type A(H3N2), followed by type A(H1N1)pdm09 and type B/Victoria. RSV activity has shown a decline, remaining at low levels. SARS-CoV-2 activity has remained low compared to previous waves, although it has been on the rise. By country: In Canada, SARS-CoV-2 activity has continued to increase, although it remains at low levels. Influenza activity has dropped below the epidemic threshold, and RSV activity has remained low. In Mexico, influenza circulation has fallen below the epidemic threshold, and SARS-CoV-2 activity has shown a slight increase, remaining at low levels. In the United States, both ILI cases and hospitalization rates for influenza, RSV, and SARS-CoV-2 remain low. While influenza and RSV activity is low, the SARS-CoV-2 positivity rate has shown an increase. Caribbean: ILI cases have increased, associated with a higher proportion of positive cases of SARS-CoV-2 and influenza. On the other hand, although SARI cases have remained at low levels, there has been an increase in the proportion of positive cases of SARS-CoV-2. Influenza activity has remained at intermediate levels during the last four EWs. During this period, the predominant viruses have been type A(H3N2), with concurrent circulation of influenza A(H1N1)pdm09. RSV activity has remained low. SARS-CoV-2 activity has shown a marked increase in the last two weeks, reaching elevated levels compared to previous waves. By country: Influenza activity has been observed over the last four EWs in the Dominican Republic, Jamaica, Guyana, and the Cayman Islands. SARS-CoV-2 activity has been noted in Jamaica, Saint Lucia, Suriname, Barbados, Guyana, the Cayman Islands, and Saint Vincent and the Grenadines. Central America: Both ILI and SARI activity have increased over the last four EWs, with most positive cases attributable to influenza. Influenza activity has risen during this period, reaching epidemic levels in several countries in the subregion. In the last four EWs, the predominant influenza viruses have been type A(H3N2), with concurrent circulation of A(H1N1)pdm09. RSV and SARS-CoV-2 activity have remained at low levels. By country: In El Salvador, influenza circulation has risen to high activity levels, and SARS-CoV-2 has shown an increase, although it remains low compared to previous waves. In Guatemala, during the last four EWs, ILI and SARI activity have fluctuated around the epidemic threshold. Most positive cases are attributed to influenza, which is at epidemic levels and declining, and RSV, whose activity is increasing. In Honduras, during the last four EWs, SARI activity has been fluctuating and remains at epidemic levels. This is mainly associated with positive influenza cases, currently at moderate levels, and to a lesser extent, SARS-CoV-2, which is increasing. In Nicaragua, a moderate increase above the epidemic threshold for influenza activity has been observed, while RSV and SARS-CoV-2 circulation remains low. In Panama, ILI and SARI cases have shown an increase over the last four EWs, coinciding with influenza activity rising to extraordinary levels. Andean: ILI and SARI activity have remained stable at low levels over the past four EWs, although an increase in the proportion of positive RSV and influenza cases has been observed. Influenza activity has remained low over the last four EWs with a fluctuating trend. During this period, the predominant influenza viruses have been type A(H3N2), with concurrent circulation of A(H1N1)pdm09. RSV activity has remained at moderate levels, with a growing trend. SARS-CoV-2 activity has remained low, showing a slight increase. By country: In Bolivia, SARI cases are in decline, with levels below the epidemic threshold. Almost all positive cases are attributable to influenza, whose activity has decreased to below the epidemic threshold after having reached moderate levels. In Colombia, SARI activity has remained at epidemic levels during the last four weeks, with most positive cases attributable to RSV (whose activity is at intermediate levels compared to previous seasons) and, to a lesser extent, influenza (whose activity is below the epidemic threshold). Acute Respiratory Infection (ARI) cases have reached extraordinary levels. In Ecuador, SARI activity remains at epidemic levels and shows an increase, while pneumonia levels have risen to moderate levels. Positive SARI cases are primarily attributable to influenza, whose increasing activity has surpassed the epidemic threshold. To a lesser extent, they are attributable to RSV, which is declining, and SARS-CoV-2, which is increasing. In Peru, influenza activity remains below the epidemic threshold, while RSV and SARS-CoV-2 activity also remain low. In Venezuela, during the last four EWs, fluctuating influenza activity around the epidemic threshold has been observed. Brazil and the Southern Cone: After the increase observed in previous weeks, SARI activity has declined over the last four EWs, with most positive cases attributable to influenza and RSV. ILI activity continues to rise, with most positive cases attributed to influenza. Influenza activity has increased over the last four EWs, reaching epidemic levels in most countries. During this period, the predominant influenza viruses have been type A(H3N2), with lesser circulation of A(H1N1)pdm09. RSV activity has remained low but has shown a slight increase. SARS-CoV-2 activity has continued to decline, staying at low levels. By country: In Argentina, ILI activity, after reaching moderate levels, has shown a slight decrease, while SARI activity continues to rise, around the epidemic threshold. Influenza activity has shown an increase, reaching extraordinary levels. There has also been an increase in the RSV positivity rate. In Brazil, after moderate SARI activity in previous weeks, it has now declined below the epidemic threshold. The highest proportion of positive cases is attributable to RSV, followed by influenza. Meanwhile, ILI cases, which had previously reached high levels, have begun to decline, with influenza responsible for the majority of positive results. In Chile, both ILI and SARI cases have reached extraordinary and epidemic levels respectively and are currently in decline; most positive cases are attributable to influenza, which, after reaching extraordinary levels, has decreased to epidemic levels. In Paraguay, SARI activity is at moderate levels, while ILI activity is around the epidemic threshold. Most positive cases are attributable to influenza, circulating at moderate levels, and to a lesser extent, RSV, which is circulating at levels below those observed in previous seasons. In Uruguay, SARI activity, after reaching high levels, has decreased to intermediate levels, with most positive cases attributable to influenza. After reaching moderate levels, influenza has decreased to epidemic levels. To a lesser extent, cases are also attributable to RSV, which is currently circulating at levels below those observed in previous seasons.