Weekly Updates: Influenza, SARS-CoV-2, RSV and other respiratory viruses - Epidemiological Week 44 (10 November 2023)

North America: Influenza activity has remained at low levels, albeit with a slight increase. During the last four epidemiological weeks (EWs), the predominant influenza viruses have been influenza A(H1N1)pdm09, with concurrent circulation of influenza B/Victoria and, to a lesser extent, influenza A(H3N2). Respiratory syncytial virus (RSV) activity has shown a slight increase in the last EW but remains at low levels. SARS-CoV-2 activity continues at moderate levels, showing a slight decrease in the last four EWs. Cases of influenza-like illness (ILI) have remained low, while severe acute respiratory infection (SARI) cases have shown an increase, with both cases associated with positive influenza results in the last four EWs. In Canada, SARS-CoV-2 activity remains high but is decreasing, with a slight increase in RSV activity in the last three EWs. In Mexico, influenza circulation has remained at epidemic levels, and SARI activity has increased to moderate levels, associated with an increase in the percentage of positive influenza cases in the last four EWs. In the United States, a slight increase in influenza activity has been observed, although it remains below the epidemic threshold. 

Caribbean: Influenza activity has increased in the last two EWs to moderate levels. During this period, the predominant viruses have been influenza A(H1N1)pdm09, followed by influenza A(H3N2) and influenza B/Victoria. RSV activity has also increased to moderate levels. SARS-CoV-2 activity, although continuing to decline, remains at moderate levels. Cases of ILI and SARI have remained stable in the last four EWs, with a higher proportion of SARI cases associated with SARS-CoV-2. Belize has experienced a pronounced increase in influenza activity in the last four EWs, reaching extraordinary levels and currently standing at moderate levels. The Dominican Republic continues to have elevated activity for RSV in the last four EWs; however, SARI activity has decreased in the last EW below the epidemic threshold. In Haiti, epidemic SARI activity has continued in the last four EWs, with positivity rates for influenza and SARS-CoV-2 on the rise. In Jamaica, SARS-CoV-2 activity continues to decline with low levels of circulation, while RSV and influenza continue to rise in the last two EWs, with pneumonia levels at the threshold of moderate activity. Saint Lucia continues to present elevated levels of SARSCoV- 2 activity and an increase in RSV and influenza activity, with SARI activity above the elevated activity threshold. In Barbados, influenza activity remains at intermediate levels and is increasing along with RSV activity in the last EW, while SARS-CoV-2 activity continues to decline.

Central America: Influenza activity has remained stable at low levels in the last four EWs. During this period, the predominant influenza viruses have been influenza B/Victoria, with concurrent circulation to a lesser extent of influenza A(H1N1)pdm09 and influenza A(H3N2). RSV activity has continued to decline in the last four EWs at moderate levels. SARS-CoV-2 activity is at low levels. The number of newly detected ILI and SARI cases has remained low; however, the proportion of SARI cases attributable to RSV has remained high in the last four EWs. In El Salvador, RSV activity has decreased to intermediate levels, SARS-CoV-2 activity has remained low in the last four EWs, and influenza activity has remained at epidemic levels during the last EW. In Guatemala, RSV activity has remained high in the last four EWs, and SARI cases, mostly positive for RSV, are also decreasing. In Honduras, RSV activity has remained at moderate levels in the last four EWs, with the majority of positive SARI cases attributable to RSV. Influenza activity has shown a pronounced increase, reaching moderate levels in the last EW. In Nicaragua, influenza activity remains at epidemic levels, showing a decrease in the last two EWs. In Panama, RSV activity continues at high levels of circulation and is increasing. 

Andean Region: Influenza activity remains at low levels of circulation. During the last four EWs, the predominant influenza viruses have been influenza A(H1N1)pdm09 followed by influenza B/Victoria. RSV activity fluctuates at low levels. SARS-CoV-2 remains at moderate activity levels with a slight increase in the last two EWs. ILI and SARI activity in the subregion continue at low levels. In Bolivia, SARSCoV- 2 circulation continues to be high; however, SARI levels are decreasing and at epidemic levels in the last four EWs. In Ecuador, SARS-CoV-2 continues to decline, and influenza activity has risen to epidemic levels in the last three EWs. In Colombia, SARS-CoV-2 and RSV activity remains at low levels with a decreasing trend in the last four EWs. In Peru, SARS-CoV-2 activity remains low and is decreasing in the last three EWs. In Venezuela, epidemic levels of influenza activity have been detected with a decrease in the last three EWs. 

Brazil and Southern Cone: Influenza activity remains at low levels of circulation. During the last four EWs, the predominant influenza viruses have been mainly influenza B/Victoria, with simultaneous circulation of influenza A(H1N1)pdm09. RSV activity remains at low levels. SARS-CoV-2 activity continues to increase with intermediate to high levels of circulation. Both ILI and SARI activity have remained low in the last four EWs, with the majority of positive cases attributable to SARS-CoV-2. Argentina has presented moderate and decreasing SARS-CoV-2 activity during the last four EWs, and influenza activity has shown a slight increase, with ILI and SARI levels below the epidemic threshold. In Brazil, SARS-CoV-2 activity continues to rise, reaching high levels. In Chile, a pronounced increase in SARS-CoV-2 activity continues, with very high levels of circulation and an increase in influenza activity above the epidemic threshold, resulting in moderate ILI levels and epidemic levels of SARI in the last four EWs. In Paraguay, SARS-CoV-2 circulation, although low, has increased in the last three EWs, and SARI activity remains at moderate levels, with the majority of positive cases attributable to SARSCoV- 2 in the last four EWs. In Uruguay, SARI activity continues to decrease in the last four EWs, with epidemic levels, and the majority of cases are associated with SARS-CoV-2, which has shown an increase in the positivity rate in the last three EWs.