Regional Update, Influenza and Other Respiratory Viruses. Epidemiological Week 47 (1 December 2023) 

ABSTRACT

[WEEKLY SUMMARY]. North America Influenza activity has remained at low levels but is on the rise. Over the past four epidemiological weeks (EW), the predominant influenza viruses have been influenza A(H1N1)pdm09, accompanied by concurrent circulation of influenza B/Victoria and, to a lesser extent, influenza A(H3N2). Respiratory syncytial virus (RSV) activity has continued to climb in the last four EW, reaching intermediate levels compared to previous seasons. SARS-CoV-2 activity remains at moderate levels, showing stability in the most recent four EW. Cases of influenza-like illness (ILI) and severe acute respiratory infection (SARI) have increased in the last four EW, with SARI cases linked to a rise in the proportion of positive cases for influenza. In Canada, SARS-CoV-2 activity has remained high in the last four EW, with an increase in influenza activity above the epidemic threshold, as well as RSV during this period. In Mexico, influenza circulation has remained at epidemic levels with a growing trend in the last four EW, and SARI activity has increased to moderate levels, associated with an increase in the percentage of positive influenza cases in the last four EW. In the United States, there has been a slight increase in influenza activity, surpassing the epidemic threshold. Caribbean Influenza activity has remained fluctuating at moderate levels over the last four epidemiological weeks (EW). During this period, the predominant viruses have been influenza A(H1N1)pdm09, followed by influenza A(H3N2) and, to a lesser extent, influenza B/Victoria. RSV activity, after an increase in previous EW, has experienced a decline in the last four EW. SARS-CoV-2 activity continues to decrease, reaching low levels in the last EW. Cases of ILI and SARI have declined in the last four EW, with a higher proportion of SARI cases associated with influenza. Belize has shown a significant decrease in influenza activity in the last two EW, reaching moderate levels. In the Dominican Republic, RSV activity has experienced a pronounced decline in the last four EW, reaching moderate levels in the last EW. In Haiti, SARI activity has fallen below the epidemic threshold, with influenza levels also below that threshold. In Jamaica, an increase has been observed in the last two EW in RSV, influenza, and SARS-CoV-2 activity, with moderate pneumonia levels and epidemic acute respiratory infection (ARI) levels. Saint Lucia continues to present high levels of SARS-CoV-2 activity, coinciding with a sudden increase in SARI activity above the threshold for extraordinary activity in the last EW. In Barbados, influenza activity remains at intermediate levels and is rising, RSV activity remains stable at intermediate levels, and SARS-CoV-2 activity continues at low levels. Central America Influenza activity, although at low levels, has increased in the last four epidemiological weeks (EW) in Central America. During this period, the predominant influenza viruses have been influenza B/Victoria, with concurrent circulation of influenza A(H1N1)pdm09 and influenza A(H3N2) to a lesser extent. RSV activity has remained at moderate to high levels in the last four EW. SARS-CoV-2 activity is at low levels. Although the number of new ILI and SARI cases has remained low, the proportion of SARI cases attributable to RSV has remained high in the last four EW. In El Salvador, RSV activity has declined to intermediate-low levels, SARSCoV- 2 activity has remained low in the last four EW, and influenza activity has continued to rise, reaching moderate levels in the last EW. In Guatemala, RSV activity has declined in the last four EW to moderate levels, with a decrease in RSV-positive SARI cases. There has been a slight increase in influenza activity above the epidemic threshold, coinciding with moderate ILI levels associated with influenza. In Honduras, RSV activity has shown a decline in the last four EW, while influenza activity has increased to epidemic levels. Although ILI and SARI cases continue to decline, influenza-positive cases have increased in the last four EW. In Nicaragua, influenza activity has remained at epidemic levels in the last four EW, with an upward trend, and RSV activity has continued to rise, reaching intermediatehigh levels in this period. In Panama, RSV activity remains at high levels, while ILI and SARI levels have shown a decline in the last four EW, with most cases positive for RSV and SARS-CoV-2. Andean Region Influenza activity has remained stable at low circulation levels in the Andean Region. Over the last four epidemiological weeks (EW), the predominant influenza viruses have been influenza A(H1N1)pdm09 followed by influenza B/Victoria. RSV activity has fluctuated at low levels. SARS-CoV-2 activity has remained at moderate levels in the last four EW. ILI and SARI activity in the subregion continue at low levels. In Bolivia, SARS-CoV-2 circulation remains high, and SARI cases have remained at epidemic levels in the last EW. In Ecuador, SARS-CoV-2 remains at moderate levels, and influenza activity continues to rise sharply, reaching moderate levels, accompanied by an increase in SARI cases positive for influenza. In Colombia, SARS-CoV-2, RSV, and influenza activity remain fluctuating at low levels in the last four EW. However, there has been an increase in SARI cases positive for RSV and, to a lesser extent, influenza in the last four EW. In Venezuela, fluctuating levels of influenza activity above the epidemic threshold have been detected in the last four EW. Brazil and Southern Cone Influenza activity remains at low circulation levels in Brazil and the Southern Cone. Over the last four epidemiological weeks (EW), the predominant influenza viruses have been primarily influenza B/Victoria, with simultaneous circulation to a lesser extent of influenza A(H1N1)pdm09 and influenza A(H3N2). RSV activity remains at low levels. SARS-CoV-2 activity has remained constant at intermediate-high levels in the last four EW. Both SARI and ILI activity have remained low in the last four EW, with most positive cases attributable to SARS-CoV-2 and, in the last EW, to influenza. Argentina has presented moderate and decreasing SARS-CoV-2 activity in the last four EW, with ILI and SARI levels below the epidemic threshold. In Brazil, SARS-CoV-2 activity continues at high levels, although with a slight decrease in the last four EW. In Chile, very high SARS-CoV-2 activity continues, with an increase in influenza activity above the epidemic threshold, resulting in moderate ILI levels and epidemic levels of SARI in the last four EW. In Paraguay, SARS-CoV-2 circulation, although declining, remains at moderate levels, with SARI activity at epidemic levels, and most positive cases attributable to SARS-CoV-2. In Uruguay, SARI activity continues to decline in the last four EW, with levels below the epidemic threshold, and most positive cases associated with SARS-CoV-2, whose positivity rate has decreased during this period.