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Weekly updates, Influenza Epidemiological Week 27 (14 July 2023)

Weekly updates, Influenza Epidemiological Week 27 (14 July 2023)
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North America: Influenza activity has remained at low levels. During the last 4 epidemiological weeks (EW), the predominant influenza viruses have been B/Victoria, with a lesser circulation of influenza A (mostly A(H1N1)pdm09). Respiratory syncytial virus (RSV) activity has remained low. SARS-CoV-2 activity has shown an increase in the last 4 EW and continues to circulate at moderate levels. Cases of influenza-like illness (ILI) and severe acute respiratory infection (SARI) have shown a decreasing trend, with the majority of these cases associated with SARS-CoV-2 and, to a lesser extent, influenza.

Caribbean: After an increase in previous weeks, influenza activity has shown a decreasing trend in the last EW. During the last 4 EW, the predominant influenza viruses have been B/Victoria, with a lesser circulation of influenza A, mainly A(H1N1)pdm09. RSV activity has remained low. SARS-CoV-2 activity has shown an increase in the last EW and currently circulates at intermediate levels. Cases of ILI and SARI, which increased due to positive cases of SARS-CoV-2 and influenza in previous EW, have shown a decreasing trend in the last 4 EW.

Central America: Influenza activity has shown a pronounced increase in the last 4 EW, with high circulation levels and a slight decline in the last 2 EWs. During the last 4 EW, the predominant influenza viruses have been type A, mainly A(H1N1)pdm09, with concurrent circulation, to a lesser extent, of influenza A(H3N2) and influenza B/Victoria. RSV activity has remained low. SARS-CoV-2 activity has remained low. ILI activity has remained low, with the majority of cases associated with influenza and SARS-CoV-2. SARI activity, although currently decreasing, showed an increase in the last 4 EWs, with the majority of cases associated with influenza and, to a lesser extent, RSV and SARS-CoV-2. In Costa Rica, extraordinary levels of influenza positivity have been observed, coinciding with concurrent circulation of SARS-CoV-2, showing a decline for both in the last 2 EWs; however, ILI and SARI levels have remained low, with the majority of cases associated with influenza and, to a lesser extent, SARS-CoV-2. In El Salvador, extraordinary levels of influenza positivity have been reported in the last 4 EW, although currently decreasing, with epidemic levels of reported SARI cases. In Honduras, after reaching high percentages of influenza positivity in previous EWs, a decline has been observed in the last 2 EW. Currently, SARI cases are decreasing, with all positives related to influenza. In Nicaragua and Panama, an increase in influenza positivity has also been observed in the last EWs, reaching moderate levels of intensity in both countries and currently decreasing. In Guatemala, an increase in RSV activity has been observed, with ILI and SARI activity above the epidemic threshold, with the majority of cases testing positive for influenza and RSV.

Andean region: Influenza activity remains stable at low levels. During the last 4 EWs, the predominant influenza viruses have been influenza A, mostly A(H1N1)pdm09, with a lesser circulation of influenza B/Victoria. RSV activity remains at low levels. SARS-CoV-2 has shown an increase, circulating at moderate levels. SARI activity, after a slight increase, with the majority of cases associated with influenza and, to a lesser extent, RSV and SARS-CoV-2, is currently decreasing. ILI activity has shown a decreasing trend, with the majority of cases associated with influenza. In Ecuador, elevated levels of SARI associated with influenza and, to a lesser extent, SARS-CoV-2 and RSV have been detected.

Brazil and Southern Cone: Influenza activity has decreased to low circulation levels. During the last 4 EW, the predominant influenza viruses have been mainly A(H1N1)pdm09, with simultaneous circulation of influenza B/Victoria. RSV activity has declined in the last 4 EW, reaching low circulation levels. SARS-CoV-2 activity has remained low. After reaching a peak, both SARI and ILI activity have continued to decline in the last 4 EW, with the majority of cases testing positive for RSV and influenza in the case of SARI, and influenza in ILI cases. In Argentina, a pronounced increase in influenza activity has been observed in the last 4 EW, reaching high levels (with a sharp decline in the last 2 EW), with the majority of cases detected positive for influenza A(H1N1)pdm09. After reaching moderate levels of ILI activity, it is currently decreasing. In Chile, after extraordinary levels of ILI activity, with the majority of cases related to RSV and influenza, activity has declined in the last 4 EW, currently at moderate levels. Also, after reaching moderate levels of SARI activity, it is currently decreasing at epidemic levels, with RSV being the most common cause among positive cases. The majority of deaths detected among SARI cases in the last EW have been positive for RSV and, to a lesser extent, SARS-CoV-2. In Paraguay, extraordinary levels of SARI activity continue, with RSV being the main cause among positive cases, currently decreasing. In Uruguay, an increase in SARI activity has been detected in the last 4 EW, remaining at moderate levels, with the majority of cases associated with RSV and influenza.