Regional Update, Influenza and Other Respiratory Viruses. Epidemiological Week 4 (2 February 2024)

ABSTRACT

[WEEKLY SUMMARY]. Regional Situation Over the past four epidemiological weeks (EWs), there has been a decline in the activity of Influenza-Like Illnesses (ILIs) in the Americas region, reaching low levels, along with a decrease in Severe Acute Respiratory Infections (SARIs), both associated with positive cases of influenza and SARS-CoV-2. ILI activity has been primarily related to moderate activity observed in North America and the Caribbean, which is currently declining, while SARI activity has been particularly influenced by moderate activity in North America. Regarding the circulation of respiratory viruses, moderate activity of SARS-CoV-2 has been maintained at the regional level compared to previous epidemic waves. Additionally, epidemic activity of influenza has been observed for this time of year with a decreasing trend, and moderate activity of Respiratory Syncytial Virus (RSV) has shown a slight decrease. North America ILI cases have shown a marked decrease, with most cases attributable to influenza, although there has also been a decrease in this proportion. Similarly, SARI cases have decreased, with most cases attributable to influenza and to a lesser extent to SARS-CoV-2. Influenza activity has remained at epidemic circulation levels, with a decrease in the last four EWs. During this period, the predominant influenza viruses have been type A(H1N1)pdm09, with concurrent circulation of influenza B/Victoria and, to a lesser extent, influenza A(H3N2). RSV activity has shown a slight decrease in the last four EWs, remaining at moderate levels. SARS-CoV-2 activity continues at moderate levels, showing a decrease in the last four EWs. By country In Canada, SARS-CoV-2 activity has remained high in the last four EWs, although showing a decreasing trend. Influenza activity has also shown a decrease but remains above the epidemic threshold, and RSV activity has remained stable at high levels during this period. In Mexico, influenza circulation has remained fluctuating at epidemic levels in the last four EWs, and a slight increase in SARS-CoV-2 circulation has been observed. In the United States, influenza activity has remained above the epidemic threshold with a slight increase in the last EW, and RSV and SARS-CoV-2 activity, although remaining at high levels, have shown a decreasing trend. Hospitalization rates for influenza, RSV, and SARS-CoV-2, after reaching similar high levels to the previous season, have shown a downward trend in the last four EWs Caribbean ILI cases have shown an increase in the last four weeks associated with an increase in positive cases of influenza, while SARI cases have remained on the decline. Influenza activity has shown a decrease in the last four EWs, reaching intermediate levels of circulation. During the last four EWs, the predominant viruses have been type A(H1N1)pdm09, followed by A(H3N2) and, to a lesser extent, B/Victoria. RSV activity has remained at low levels. SARS-CoV-2 activity has increased in the last four EWs, reaching high levels. By country Elevated influenza activity has been observed in the Dominican Republic, Jamaica, Saint Lucia, the Cayman Islands, and Saint Vincent and the Grenadines. Elevated SARS-CoV-2 activity has been observed in Belize, the Dominican Republic, Dominica, Jamaica, Saint Lucia, Barbados, the Cayman Islands, Guyana, and Saint Vincent and the Grenadines. Central America ILI cases have shown an increase in the last four weeks, with most positive cases attributable to SARS-CoV-2 and, to a lesser extent, influenza. SARI cases have also shown an increase, with a slight increase in the proportion of positive cases for SARS-CoV-2. Influenza activity has increased in the last four EWs, reaching moderate levels. During this period, the predominant viruses have been type A(H1N1)pdm09, followed by B/Victoria and, to a lesser extent, A(H3N2). RSV activity has decreased to low levels. SARS-CoV-2 activity, although remaining at low levels, has increased in the last four EWs. By country In El Salvador, SARS-CoV-2 activity has shown a marked increase in the last three EWs, reaching high levels. In Guatemala, an increase in ILI cases associated with influenza and, to a lesser extent, SARS-CoV-2 has been observed, with activity levels considered moderate, while SARI cases have also shown a slight increase, with positive cases attributable to both influenza and RSV, also at epidemic levels. In Honduras, a slight increase has been observed in both ILI and SARI cases associated with positive influenza cases, with activity fluctuating around epidemic levels. In Nicaragua, RSV activity has shown a decrease to low levels in the last four weeks. In Panama, SARS-CoV-2 activity has shown a decrease after reaching high levels, and influenza activity has fluctuated around the epidemic threshold in the last four EWs. ILI and SARI cases have shown an increase in the last four EWs, with most positive cases attributable to SARS-CoV-2. Andean ILI activity has remained stable at low levels, while SARI cases have shown an increase associated with an increase in positivity for SARS-CoV-2, influenza, and RSV. Influenza activity has remained at low levels in the last four EWs. During this period, the predominant influenza viruses have been type A(H1N1)pdm09, with circulation of B/Victoria and A(H3N2) to a lesser extent. RSV activity has remained at low levels. SARS-CoV-2 activity has remained at high levels. By country In Bolivia, SARS-CoV-2 circulation has remained high. In Colombia, SARS-CoV-2 activity has shown a pronounced increase in the last four EWs, reaching high levels, with SARI cases increasing associated with positive cases of influenza followed by SARS-CoV-2 and RSV. In Ecuador, SARS-CoV-2 activity remains active, while influenza activity has continued to decrease around the epidemic threshold, and RSV activity has shown a slight increase in the last four EWs. This has been accompanied by an increase in SARI cases in the last four EWs, with epidemic levels in the last EW, with most positive cases predominantly for influenza and SARS-CoV-2 and, to a lesser extent, RSV. In Venezuela, fluctuating activity of influenza and RSV has been observed. Brazil and the Southern Cone SARI and ILI activity has remained low in the last four EWs, with the majority of positive cases attributable to SARS-CoV-2 with a rising percentage of positive cases. Influenza activity has remained at low circulation levels in the last four EWs. 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. SARSCoV- 2 activity has continued to rise at high levels. By country In Argentina, ILI and SARI levels have remained below the epidemic threshold. However, an increase in SARS-CoV- 2 positivity has been observed, reaching high levels in the last four EWs. In Brazil, SARS-CoV-2 activity has remained stable at high levels during this period. In Chile, a decrease in SARS-CoV-2 activity has been observed, with ILI cases at epidemic levels and SARI cases below this threshold, mostly attributable to SARS-CoV-2 and, to a lesser extent, influenza. In Paraguay, SARSCoV- 2 circulation has remained high in the last four EWs, and influenza activity has decreased below the epidemic threshold, while SARI activity has remained at epidemic levels with the majority of positive cases attributable to SARS-CoV-2. In Uruguay, SARI activity has continued below the epidemic threshold, with the majority of the few positive cases attributable to SARSCoV- 2.