Weekly updates, Influenza Epidemiological Week 32 (18 August 2023)

North America: Influenza activity has remained at low levels. Over the past 4 epidemiological weeks (EW), the predominant influenza viruses have been influenza A(H1N1)pdm09, with concurrent circulation of influenza B/Victoria. Respiratory syncytial virus (RSV) activity has stayed at low levels. The activity of SARS-CoV-2 has shown an increase over the last 4 EWs and continues to circulate at moderate levels. Cases of influenza-like illness (ILI) and severe acute respiratory infection (SARI) have seen a slight increase, with the majority of these cases associated with SARS-CoV-2 and to a lesser extent with influenza. In Mexico, epidemic levels of influenza circulation have been detected, which are decreasing.

Caribbean: Influenza activity continues to show a decreasing trend over the past 4 EWs, with a predominance of influenza B/Victoria and, to a lesser extent, circulation of influenza A, mainly A(H1N1)pdm09. RSV activity has remained low. The activity of SARS-CoV-2 has shown an increasing trend over the last three EWs, with intermediate levels of circulation, especially in Barbados, Grenada, Guyana, Jamaica, and Saint Lucia. ILI and SARI cases have displayed a decreasing trend in the past 4 EWs.

Central America: After reaching a peak in previous weeks, influenza activity has continued to decline over the last 4 EWs. During this period, the predominant influenza viruses have been influenza B/Victoria with concurrent circulation of influenza A, mainly A(H1N1)pdm09, and to a lesser extent, influenza A(H3N2). RSV activity has increased in the last 4 EWs, reaching intermediate to high levels of circulation. The activity of SARS-CoV-2 has remained low. ILI activity has remained low, with the majority of cases associated with influenza. SARI activity is currently declining, with the majority of cases associated with RSV. In Costa Rica, extraordinary levels of influenza positivity are detected with concurrent circulation of SARS-CoV-2. ILI and SARI levels remain low, with the majority of cases associated with influenza and, to a lesser extent, with SARS-CoV-2. In El Salvador, influenza activity is decreasing, with epidemic levels in reported SARI cases. Additionally, there has been an increase in RSV positivity levels with elevated activity. In Honduras, after reaching elevated levels in the percentages of influenza positivity, the last 4 EWs have seen a decline to levels below the epidemic threshold. ILI and SARI cases are currently decreasing, with almost all positive cases related to influenza. In Guatemala, RSV activity continues to rise with moderate to high levels, and ILI cases are mostly positive for influenza, while SARI cases are positive for RSV. In Nicaragua and Panama, after achieving moderate activity levels in previous EWs, influenza positivity in both countries is currently at epidemic levels.

Andean region: Influenza activity remains stable at low levels. Over the last 4 EWs, the predominant influenza viruses have been influenza A, predominantly A(H1N1)pdm09, with lesser circulation of influenza B/Victoria. RSV activity remains at low levels. SARSCoV- 2 has shown a decline over the last 4 EWs, circulating at low levels, although circulation remains elevated in Bolivia. SARI activity continues to decline, with most cases associated with influenza and, to a lesser extent, RSV and SARS-CoV-2. ILI activity has shown a decreasing trend, with most cases associated with influenza.

Brazil and Southern Cone: Influenza activity has decreased to low levels of circulation. Over the past 4 EWs, the predominant viruses have been primarily influenza A(H1N1)pdm09, with simultaneous circulation of influenza B/Victoria. RSV activity has declined in the last 4 EWs, reaching low levels of circulation. SARS-CoV-2 activity has remained low, albeit with a slight increase. Both SARI and ILI activities have continued to decline over the past 4 EWs. Argentina continues to experience epidemic levels of influenza activity, with the majority of detected cases being positive for influenza A(H1N1)pdm09 and ILI and SARI levels below the epidemic threshold. In Brazil, influenza and RSV activity remains low, while SARS-CoV-2 has shown a slight increase in the last EW. In Chile, ILI activity has increased, remaining at moderate levels, with the majority of positive cases related to influenza. In Paraguay, SARI activity remains high, with RSV being the primary cause among positive cases, followed by SARS-CoV-2. In Uruguay, SARI activity remains at epidemic levels, with the majority of cases associated with RSV.