Regional Update, Influenza and Other Respiratory Viruses. Epidemiological Week 25 (28 June 2024)

[WEEKLY SUMMARY]. Regional Situation: During the last four epidemiological weeks (EWs), low levels of Influenza-Like Illness (ILI) activity have been observed in the Americas. However, there has been epidemic activity in the Southern Cone and increased activity in the Caribbean and Central America subregions. This activity is associated with the circulation of influenza in the Southern Cone, Central America, and the Caribbean, 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 and Central America. This 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. Similarly, there has been an increase in 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, and the Southern Cone where an increase has been noted. North America: ILI cases and hospitalizations associated with respiratory viruses have remained at low levels during the last four EWs. Influenza activity has continued to decline, staying below the epidemic threshold in all countries. 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 remained low. SARS-CoV-2 activity has been increasing, although it remains at low levels compared to previous waves. By country: In Canada, SARS-CoV-2 activity has been increasing but remains at low levels. Influenza activity has dropped below the epidemic threshold, and RSV activity has remained low. In Mexico, influenza circulation has decreased 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: Over the past four EWs, ILI cases have increased, associated with a higher proportion of positive SARS-CoV-2 and influenza cases. Meanwhile, although SARI cases have remained at low levels, there has been an increase in both the count and proportion of positive SARS-CoV-2 cases. Influenza activity has remained at intermediate levels 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, Guyana, and the Cayman Islands. SARS-CoV-2 activity has been noted in Belize, the Dominican Republic, Jamaica, Saint Lucia, Suriname, Barbados, Guyana, the Cayman Islands, and Saint Vincent and the Grenadines. Central America: After showing an increase in previous weeks in ILI and SARI activity, a decline has been observed over the past three 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 influenza A(H1N1)pdm09. RSV and SARS-CoV-2 activity have remained at low levels. By country: In El Salvador, influenza circulation has risen to extraordinary levels, and SARS-CoV-2, after showing a slight increase, remains at low levels compared to previous waves. In Guatemala, an increase above the epidemic threshold has been observed in ILI and SARI activity. Most positive ILI cases are attributable to influenza, which is at epidemic levels and declining, while SARI cases are mainly due to RSV, whose activity is increasing. In Honduras, during the last four EWs, SARI activity has been fluctuating and remains at epidemic levels. This is primarily associated with positive influenza cases, currently at moderate levels, and to a lesser extent, SARS-CoV-2, which is increasing. In Nicaragua, an increase above the moderate 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 high levels. Andean Region: ILI and SARI activity has remained stable at low levels over the past four EWs. However, there has been an increase in the proportion of positive cases for RSV and influenza. Influenza activity has remained low during this period, with a fluctuating trend. 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. Nearly all positive cases are attributable to influenza, whose activity has decreased to below the epidemic threshold after reaching moderate levels. In Colombia, SARI activity, after reaching epidemic levels in recent weeks, has declined below this threshold. Most positive cases are attributable to RSV, which is at intermediate levels compared to previous seasons, and to a lesser extent, influenza, which is below the epidemic threshold. Acute Respiratory Infection (ARI) cases have reached extraordinary levels. In Ecuador, SARI activity has shown a marked increase in the last EW, reaching high levels, while pneumonia levels have risen to moderate levels. Most positive SARI cases are attributable to influenza, whose activity is increasing and 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, after reaching epidemic activity in previous weeks, a decline below this threshold has been observed. Brazil and the Southern Cone: Following the increase observed in previous weeks, ILI and SARI activity has declined over the last four EWs, with most positive cases attributable to influenza and RSV, respectively. Influenza activity remains at epidemic levels in most countries, although it is 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, although rising, has remained at low levels compared to previous seasons. SARS-CoV-2 activity has stayed at low levels. By country: In Argentina, ILI activity, after reaching moderate levels, has decreased to epidemic levels, while SARI activity has remained around the epidemic threshold. Influenza activity has reached extraordinary levels but is showing a slight decrease. At the same time, an increase in RSV positivity has been observed, although still below the peak levels of previous seasons. In Brazil, ILI and SARI activity have decreased to below the epidemic threshold, with the highest proportion of positive cases attributed to RSV and influenza. In Chile, ILI and SARI cases, after reaching extraordinary levels this season, are currently declining to moderate and epidemic levels, respectively. Most positive cases are attributable to RSV, whose activity is increasing, although still below levels observed in previous seasons. Influenza activity, 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 moderate 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.