Regional Update, Influenza and Other Respiratory Viruses. Epidemiological Week 31 (9 August 2024)

[WEEKLY SUMMARY]. Regional Situation: During the last four epidemiological weeks (EW), there has been epidemic activity of Influenza-Like Illness (ILI) in the Southern Cone, alongside an increase in activity in the subregions of North America, the Caribbean, and Central America. This activity 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 observed in the Southern Cone, the Andean subregion, and Central America, related to positive cases of RSV, and to a lesser extent, influenza. In North America, there has been an uptick in activity related to the circulation of SARS-CoV-2. Regarding the circulation of respiratory viruses at the regional level, SARS-CoV-2 activity has increased, particularly in North America, the Caribbean, Central America, and the Andean subregion. Additionally, although influenza activity has decreased in the Southern Cone and Central America, epidemic levels persist. RSV activity has reached epidemic levels in Central America, the Andean subregion, and the Southern Cone. North America: After a rise in cases of ILI, SARI, and hospitalizations associated with respiratory viruses in recent weeks, there has been a gradual decline. However, there has been a significant increase in the proportion of positive SARS-CoV-2 cases. Influenza activity has remained below the epidemic threshold in 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. In contrast, SARSCoV- 2 activity has increased, reaching moderate or high levels in some countries compared to previous waves. By country: • In Canada, SARS-CoV-2 activity has risen, reaching levels close to the peaks observed in previous waves. Influenza activity remains below the epidemic threshold, while RSV activity remains low. • In Mexico, after reaching moderate levels in previous epidemiological weeks, ILI and SARI cases have shown a slight decline in the past week. Most positive cases are attributable to SARS-CoV-2. Both influenza and RSV activity remain low. • In the United States, the SARS-CoV-2 hospitalization rate per 100,000 inhabitants has increased in recent weeks, reaching levels similar to the peaks observed in 2023 and 2024. Influenza and RSV activity remain low. Caribbean: Over the past four EW, ILI cases have risen, linked to a higher proportion of positive influenza cases, while SARI cases have remained low. Influenza activity has fluctuated at moderate levels during the past four EW, with type A(H3N2) being predominant, followed by A(H1N1)pdm09. RSV activity has remained low, while SARS-CoV-2 activity remains stable at high levels. By country: In the last four EW, influenza activity has been observed in Belize, the Dominican Republic, Jamaica, the Cayman Islands, and Guyana. Additionally, SARS-CoV-2 activity has been recorded in Belize, Jamaica, Saint Lucia, Suriname, Barbados, Guyana, the Cayman Islands, and Saint Vincent and the Grenadines. • In Saint Lucia, there has been an increase in SARI activity, with epidemic levels linked to SARS-CoV-2 circulation, although this activity has decreased in the most recent EW. • In Guyana, there has been a rise in ILI and SARI cases, with positive cases attributable to both SARS-CoV-2 and influenza, and to a lesser extent, RSV. Central America: There has been an increase in ILI and SARI activity, with most positive cases attributable to SARS-CoV-2 and RSV, whose activity has been on the rise. Influenza activity, after reaching epidemic levels in several countries in the subregion, has declined over the past four EW. During this period, the predominant influenza viruses have been type A(H3N2). RSV activity has reached levels comparable to the peaks recorded in previous seasons. Although SARS-CoV-2 activity is increasing, it remains below the levels observed in previous waves. By country: • In Costa Rica, following the increase in ILI and SARI cases in previous weeks, a downward trend has been observed over the past four EW, with most positive cases attributable to SARS-CoV-2, whose activity is increasing, and to a lesser extent, influenza, which is currently declining within epidemic levels. • In El Salvador, influenza circulation, after reaching moderate levels, has declined over the past four EW, falling below the epidemic threshold. SARS-CoV-2 remains at low levels compared to previous waves. • In Guatemala, ILI activity has increased to moderate levels, with most positive cases attributable to influenza and SARSCoV- 2. SARI activity remains constant at epidemic levels; however, there has been a significant increase in the proportion of positive RSV cases. • In Honduras, over the past four EW, SARI activity has fluctuated between epidemic and moderate levels, mainly associated with positive influenza cases, which is currently declining within epidemic levels, and to a lesser extent, SARS-CoV-2. • In Nicaragua, after influenza circulation exceeded the elevated threshold, it has declined over the past four EW to epidemic levels, while RSV and SARS-CoV-2 circulation remains low. • In Panama, ILI and SARI cases have increased over the past four EW, with a rise in the proportion of positive RSV cases, whose activity has shown a significant increase, alongside SARS-CoV-2. Influenza activity has declined below the epidemic activity threshold. Andean: ILI and SARI activity has declined over the past four EW in most countries. Additionally, there has been an increase in the proportion of positive SARS-CoV-2 cases, with a decrease in the proportion of positive RSV and influenza cases, whose activity has continued to decline during this period. The predominant influenza viruses have been type A(H3N2). 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: • In Bolivia, SARI cases are fluctuating around the epidemic threshold. Influenza activity has decreased to levels below this threshold. • In Colombia, SARI activity, after reaching epidemic levels in recent weeks, has declined below this threshold. Most positive cases are attributed to RSV, whose activity is declining, and to a lesser extent to SARS-CoV-2, which is increasing, with intermediate circulation levels compared to previous waves. Acute Respiratory Infection (ARI) cases remain high. • In Ecuador, SARI and pneumonia activity has remained around the moderate threshold in the past four EW. Positive SARI cases are mainly attributed to influenza, which is at epidemic levels, and to a lesser extent to RSV and SARS-CoV-2. • In Peru, after reaching extraordinary levels of SARI, there has been a decline in the past week. Most positive cases are attributable to RSV, whose activity is on the rise, and to a lesser extent, influenza, which is below the epidemic threshold. Additionally, increasing SARS-CoV-2 activity has been recorded; however, it remains at low levels. • In Venezuela, a decline in influenza activity has been observed, falling below the epidemic threshold. Brazil and the Southern Cone: Following the increase observed in previous weeks, SARI activity has declined over the past four EW, with most positive cases attributable to RSV and, to a lesser extent, influenza. ILI activity has shown a slight uptick, associated with an increase in the proportion of positive SARS-CoV-2 cases. Influenza activity is declining, remaining below the epidemic threshold in most countries. During this period, the predominant influenza viruses have been type A(H1N1)pdm09 and A(H3N2). RSV activity has shown a slight decrease after reaching levels below the peaks observed in previous seasons. SARS-CoV-2 activity has remained low, although with a slight increase. By country: • In Argentina, ILI activity, after reaching high levels, has declined to levels below the epidemic threshold, while SARI activity, after reaching epidemic levels, has also fallen below this threshold. Influenza activity, after reaching high levels, has declined to epidemic levels. Additionally, there has been an increase in the RSV positivity rate, reaching values similar to the peaks observed in previous seasons. • In Brazil, ILI and SARI activity has declined to levels below the epidemic threshold. Influenza activity is also decreasing below the epidemic threshold, while RSV activity remains low. However, SARS-CoV-2 activity has shown a slight increase. • In Chile, after a previous decline, there has been a slight uptick in ILI and SARI cases, with elevated and epidemic levels, respectively. Most positive cases during the past four EW are attributable to RSV, whose activity remains on the rise, though with positivity levels below the peaks observed in previous seasons. Influenza activity, after reaching extraordinary levels, has declined below the epidemic threshold. • In Paraguay, SARI activity remains at moderate levels, with most positive cases attributable to RSV, whose activity is declining, and to a lesser extent SARS-CoV-2, which is increasing. ILI activity, after reaching epidemic levels, has declined below this threshold. • In Uruguay, SARI activity has remained at moderate levels, with most positive cases attributable to RSV, whose activity continues to rise, reaching levels higher than the peaks observed in previous seasons.