Regional Update, Influenza and Other Respiratory Viruses. Epidemiological Week 13 (5 April 2024)

[WEEKLY SUMMARY]. Regional Situation: Over the past four epidemiological weeks (EWs), intermediate levels of Influenza-Like Illness (ILI) activity have been observed in the Americas region, with a decreasing trend primarily related to moderate activity observed in North America and the Caribbean. Additionally, there has been a decrease in Severe Acute Respiratory Infection (SARI) activity, currently at low levels. In both cases, the observed activity has been associated with positive cases of influenza and SARS-CoV-2. Regarding the circulation of respiratory viruses, at the regional level, after an increase observed in previous weeks, SARS-CoV-2 activity has decreased to low levels compared to previous epidemic waves. Likewise, epidemic activity of influenza has been observed for this time of the year, remaining stable, and a declining activity of Respiratory Syncytial Virus (RSV) currently at low levels. North America: ILI cases have continued to decline during the last four EWs, with intermediate levels, and the majority of cases attributable to influenza. SARI cases and hospitalizations associated with respiratory viruses have remained on a downward trend. Influenza activity has remained at epidemic circulation levels, showing a decline during the last four EWs. During this period, the predominant influenza viruses have been type B/Victoria, with concurrent circulation of influenza A(H1N1)pdm09 and influenza A(H3N2). RSV activity has shown a decline in the last four EWs, remaining at low levels. SARS-CoV-2 activity has decreased in the last four EWs to low levels compared to previous waves. By country: In Canada, SARS-CoV-2 activity has shown a marked decrease in the last four EWs to low levels. Influenza activity has remained at epidemic levels with a gradual decline, and RSV activity has remained low. In Mexico, influenza circulation has remained fluctuating at epidemic levels in the last four EWs, and SARS-CoV-2 circulation has shown a decrease to medium-low levels. In the United States, influenza activity has shown a decrease in the last four EWs, although it remains above the epidemic threshold. Both RSV and SARS-CoV-2 have maintained a downward activity trend to low levels. ILI cases have shown a decline and remain at moderate levels. Hospitalization rates for influenza, RSV, and SARS-CoV-2 have shown a decreasing trend in the last four EWs, with low levels. Caribbean: After the increase observed in previous EWs, ILI cases have shown a decrease in the last four weeks. SARI cases have remained on a downward trend, with the majority of positive cases attributable to influenza. Influenza activity, which had been declining since previous weeks, has shown a slight increase in the last four EWs, although it remains at low circulation levels. During this period, the predominant viruses have been type A(H1N1)pdm09, with concurrent circulation, to a lesser extent, of influenza type A(H3N2) and B/Victoria. RSV activity has remained at low levels. SARS-CoV-2 activity has remained at low levels. By country: Influenza activity has been observed in Belize, Jamaica, Suriname, and the Cayman Islands. SARS-CoV-2 activity has been observed in Barbados, Saint Lucia, and Guyana. Central America: During the last four EWs, both ILI and SARI activity have remained low, although showing a slight increase, with the majority of positive cases attributable to influenza. Influenza activity has shown a slight increase during this period, reaching intermediate-low levels. In the last four EWs, the predominant influenza viruses have been type A(H1N1)pdm09, with concurrent circulation of A(H3N2), and to a lesser extent, B/Victoria. RSV and SARS-CoV-2 activity have remained at low levels. By country: In El Salvador, SARI activity is around epidemic levels with SARS-CoV-2 circulation at low levels, and influenza activity fluctuating around the epidemic threshold. In Guatemala, an increase in ILI and SARI cases associated with an increase in positive influenza cases has been observed, with moderate activity levels. In Honduras, an increase in SARI cases has been observed in the last four EWs, reaching epidemic levels, associated with an increase in positive influenza cases, with activity rising to moderate levels. In Nicaragua, the activity of both RSV, influenza, and SARS-CoV-2 is at low levels. In Panama, influenza activity is fluctuating around the epidemic threshold, and ILI and SARI cases have shown a slight increase. Andean: ILI activity has remained stable at low levels with the majority of positive cases attributable to influenza and SARSCoV- 2. SARI cases have remained on a downward trend at low levels, with the majority of positive cases attributable to RSV followed by SARS-CoV-2 and influenza. Influenza activity has remained at low levels in the last four EWs with a slightly increasing trend. During this period, the predominant influenza viruses have been type A(H1N1)pdm09, with concurrent circulation of A(H3N2) and, to a lesser extent, B/Victoria. RSV activity has remained at low levels, although with a slight increase. SARS-CoV-2 activity has remained on a downward trend at low levels. By country: In Bolivia, an increase in ILI and SARI cases associated with positive influenza cases has been observed, reaching levels around the epidemic threshold. Influenza has shown a marked increase in activity, surpassing the high threshold. In Colombia, SARS-CoV-2 activity has decreased in the last four EWs, reaching low levels, influenza, and RSV activity have shown a slight increase, although remaining low. SARI activity has remained on a downward trend around the epidemic threshold in the last four EWs, with positive cases attributable to influenza and RSV, and to a lesser extent, SARS-CoV-2. In Ecuador, SARSCoV- 2 has decreased to medium levels, influenza activity has remained below the epidemic threshold, and RSV activity continues at medium levels with a slight increase in the last four EWs. SARI activity has fluctuated around the moderate threshold, with positive cases attributable to influenza, SARS-CoV-2, and, to a lesser extent, RSV. In Venezuela, during the last EWs, fluctuating influenza activity has been observed below the epidemic threshold. Brazil and the Southern Cone: ILI and SARI activity have increased in the last four EWs, with the majority of positive cases attributable to SARS-CoV-2 and, to a lesser extent, influenza. Influenza activity has shown an increase in the last four EWs with epidemic levels in some countries. During this period, the predominant influenza viruses have been type A(H3N2), followed by A(H1N1)pdm09. RSV activity has remained at low levels. SARS-CoV-2 activity has remained on a downward trend with intermediate levels of activity. By country: In Argentina, ILI and SARI levels have remained below the epidemic threshold. Influenza activity is increasing, with levels above the epidemic threshold, and the percentage of SARS-CoV-2 positivity has remained on a downward trend at medium-low levels. In Brazil, SARS-CoV-2 activity remains on a downward trend, with medium-low levels, and influenza activity remains stable around the epidemic threshold. In Chile, both ILI and SARI cases have shown an increase in the last four EWs, reaching epidemic levels; the majority of positive cases are attributable to SARS-CoV-2 and, to a lesser extent, influenza. Moderate SARS-CoV-2 activity has been observed, and influenza activity has shown a pronounced increase surpassing the epidemic threshold. In Paraguay, SARI activity has remained around the epidemic threshold, and ILI activity has remained below this threshold. Influenza activity has shown an increase surpassing the epidemic threshold; SARS-CoV-2 circulation has shown a decrease in the last four EWs, reaching low levels, and RSV activity has remained low. In Uruguay, SARI activity has continued at levels below the epidemic threshold, with the majority of positive cases attributable to SARS-CoV-2, whose activity is at moderate levels and decreasing.