Regional Update, Influenza and Other Respiratory Viruses. Epidemiological Week 11 (22 March 2024)

ABSTRACT

[WEEKLY SUMMARY]. Regional Situation Over the past four Epidemiological Weeks (EWs), the Americas region has experienced intermediate levels of Influenza-Like Illness (ILI) activity, showing a decreasing trend. Concurrently, there has been a decline in Severe Acute Respiratory Infection (SARI) activity, currently at low levels. Both ILI and SARI activities have been associated with positive cases of influenza and SARS-CoV-2. ILI activity has been notably influenced by moderate activity in North America and the Caribbean, while SARI activity has been particularly impacted by trends in North America. Regarding respiratory virus circulation, regional SARS-CoV-2 activity has decreased after an observed increase in previous weeks, although it remains moderate compared to previous epidemic waves. Additionally, an epidemic activity of influenza has been observed for this time of year, alongside a declining activity of Respiratory Syncytial Virus (RSV), which is currently at low levels. North America Despite a slight decline in previous EWs, ILI cases have maintained medium-high levels, primarily attributed to influenza. SARI cases and respiratory virus-related hospitalizations have continued to decline. Influenza activity has remained at epidemic levels, showing a slight decrease over the past four EWs. Predominant influenza viruses during this period have been type A , with A(H1N1)pdm09 and A(H3N2) circulating concurrently, along with lesser circulation of influenza B/Victoria. RSV activity has declined over the past four EWs, maintaining moderate levels. SARS-CoV-2 activity has decreased over the same period to low levels compared to previous waves. By countries In Canada, SARS-CoV-2 activity has significantly decreased over the past four EWs to medium-low levels. Influenza activity has remained epidemic, gradually declining, while RSV activity has also decreased to moderate levels. In Mexico, influenza circulation has fluctuated at epidemic levels over the past four EWs, with SARS-CoV-2 circulation remaining at intermediate levels compared to previous waves. In the United States, influenza activity has consistently remained above the epidemic threshold, while RSV and SARSCoV- 2 activities have decreased to low levels. ILI cases have remained stable at medium levels. Hospitalization rates for influenza, RSV, and SARS-CoV-2 have shown a downward trend over the past four EWs after reaching similar elevated levels as the previous season. Caribbean Following a previous increase, ILI cases have markedly decreased over the past four weeks, primarily attributed to influenza. SARI cases have continued to decline, with most positive cases associated with influenza. Influenza activity has decreased over the past four EWs, reaching low circulation levels. Predominant viruses during this period have been influenza A(H1N1)pdm09, with concurrent circulation of A(H3N2) and B/Victoria to a lesser extent. RSV activity has remained low, and SARS-CoV-2 activity has also declined to low levels. By countries Increased influenza activity has been observed in Suriname and the Cayman Islands. Elevated SARS-CoV-2 activity has been observed in Dominica, Saint Lucia, Guyana, and Saint Vincent and the Grenadines. Central America ILI activity has remained stable at low levels, primarily attributed to influenza. SARI cases have shown a slight increase but remain at low levels, with most positive cases attributed to influenza. Influenza activity has increased to intermediate levels over the last four EWs. During this period, 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. SARS-CoV-2 activity has also remained at low levels. By countries In El Salvador, SARS-CoV-2 activity has decreased over the past four EWs to low levels, while SARI activity has remained at epidemic levels. In Guatemala, an increase in ILI cases associated with influenza has been observed, reaching moderate levels, while SARI cases have remained at epidemic levels, primarily associated with influenza. In Honduras, there has been a new increase in SARI cases, reaching epidemic levels, associated with a rise in positive cases for influenza. In Nicaragua, activity for both RSV, influenza, and SARS-CoV-2 has decreased to low levels. In Panama, influenza activity has shown a pronounced increase to moderate levels over the past four EWs, while ILI and SARI cases have remained low. have continued to decline to low levels, with the majority of positive cases attributable to SARS-CoV-2 and, to a lesser extent, influenza. Influenza activity has remained at low levels over the last four EWs. During this period, 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. SARS-CoV-2 activity has remained on the decline to moderate levels. By countries In Bolivia, an increase in ILI and SARI cases has been observed, reaching levels around the epidemic threshold associated with positive cases for influenza. Influenza has shown a marked increase in activity, surpassing the elevated threshold. In Colombia, SARS-CoV-2 activity has decreased over the last four EWs to medium-low levels; SARI activity has been around the epidemic threshold during these last four EWs, with positive cases attributable to influenza and, to a lesser extent, SARS-CoV-2 and RSV. In Ecuador, SARS-CoV-2 activity has increased to medium-high levels, influenza activity has remained below the epidemic threshold, and RSV activity has remained at moderate levels over the last four EWs. SARI activity has fluctuated around the moderate threshold, with positive SARI cases attributable to influenza, SARS-CoV-2, and, to a lesser extent, RSV. In Peru, after a marked increase in SARS-CoV-2 activity in previous weeks, a decrease has been observed in the last four EWs to low levels. In Venezuela, fluctuating influenza activity has been observed below the epidemic threshold over the last four EWs. Brazil and Southern Cone SARI and ILI activity have remained at low levels over the last four EWs, with the majority of positive cases attributable to SARS-CoV-2. Influenza activity has shown an increase over the last four EWs, reaching levels around the epidemic threshold in some countries. During this period, the predominant influenza viruses have been type A(H3N2) and A(H1N1)pdm09 followed by B/Victoria. RSV activity has remained at low levels. SARS-CoV-2 activity has remained on the decline with elevated levels. By countries In Argentina, ILI and SARI levels have remained below the epidemic threshold. The percentage of SARS-CoV-2 positivity, although remaining at moderate levels, has shown a marked decrease over the last four EWs, and influenza activity is below the epidemic threshold. In Brazil, SARS-CoV-2 activity has remained at elevated levels, albeit decreasing, and influenza activity has shown an increase during the last four EWs, surpassing the epidemic threshold. In Chile, an increase in SARS-CoV-2 activity has been observed over the last four EWs at moderate levels, along with an increase in influenza activity, which has surpassed the epidemic threshold. ILI cases have shown a pronounced increase with epidemic levels; SARI cases have slightly surpassed the epidemic threshold, with the majority of positive cases for both ILI and SARI attributable to SARS-CoV-2 and to a lesser extent, influenza. In Paraguay, the circulation of SARS-CoV-2 has shown a decrease over the last four EWs, reaching low levels, while influenza and RSV activity have remained low. ILI and SARI activity have remained below the epidemic threshold. In Uruguay, SARI activity has continued below the epidemic threshold, albeit with a slight increase in the last four weeks, with the majority of the few positive cases attributable to SARS-CoV-2.