Weekly updates, Influenza Epidemiological Week 26 (7 July 2023)

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. The activity of SARS-CoV-2 has shown a slight increase 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: Influenza activity has shown a decreasing trend. During the last 4 EWs, the predominant influenza viruses have been B/Victoria, with lesser circulation of influenza A (mainly A(H1N1)pdm09). RSV activity has remained low. SARS-CoV-2 activity after showing an increase in previous weeks, has been decreasing in the last 4 EW and is currently at intermediate levels of circulation. Cases of ILI and SARI which had increased due to positive cases of SARS-CoV-2 and influenza in previous weeks, 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 levels of circulation and showing a slight decrease in the last 2 weeks. During the last 4 EWs, the predominant influenza viruses have been influenza A, mainly A(H1N1)pdm09, with co-circulation of influenza A(H3N2) and influenza B/Victoria to a lesser extent. 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, has shown an increase in the last 4 weeks, 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 and increasing circulation of SARS-CoV-2. However, ILI and SARI levels have remained low, with most cases associated with influenza and, to a lesser extent, SARS-CoV-2. In El Salvador, elevated levels of influenza positivity have been reported, and with all positive reported ILI cases in the last 4 EW positive for influenza. In Honduras, high percentages of influenza positivity have been reached in recent weeks, with moderate levels in SARI cases, although decreasing, and all of the positive cases due to influenza. In Nicaragua and Panama, there has also been an increase in influenza positivity in recent weeks, reaching moderate levels of intensity in both countries and currently decreasing. In Guatemala, there has been an increase in RSV activity with ILI and SARI activity above the epidemic threshold, with most cases testing positive for influenza and RSV.

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

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