Regional Update, Influenza and Other Respiratory Viruses. Epidemiological Week 7 (23 February 2024)

ABSTRACT

[WEEKLY SUMMARY]. Regional Situation Over the past four Epidemiological Weeks (EWs), there has been a decline in Influenza-Like Illness (ILI) activity in the Americas region, stabilizing at medium levels. Similarly, a decrease has been observed in the activity of Severe Acute Respiratory Infection (SARI), currently at low levels. In both cases, the observed activity has been associated with positive cases of influenza and SARS-CoV-2. ILI activity has been mainly linked to moderate activity observed in North America, which showed a mild increase in the past four weeks. Regarding the circulation of respiratory viruses, SARS-CoV-2 activity has remained moderate at the regional level compared to previous epidemic waves. Influenza activity has increased over the past four weeks period; respiratory syncytial virus (RSV) activity, while remaining moderate, has also declined. North America ILI cases, after a slight decrease in previous EWs, have remained at medium-high levels, with most cases attributable to influenza, although showing a decline in this proportion. SARI cases have decreased, with most cases attributable to influenza and, to a lesser extent, SARS-CoV-2. Influenza activity has remained at epidemic levels after a slight decrease in recent EWs. During this period, the predominant influenza viruses have been type A(H1N1)pdm09, with concurrent circulation of influenza B/Victoria and, to a lesser extent, influenza A(H3N2). RSV activity has declined in the last four EWs, remaining at moderate levels. SARS-CoV-2 positivity has slightly decreased in the last four EWs and remains below late 2023 levels. By countries In Canada, SARS-CoV-2 activity has markedly decreased in the last four EWs to medium levels. Influenza activity remains at epidemic levels, and RSV activity has remained stable at high levels during this period. In Mexico, influenza circulation has remained fluctuating at epidemic levels in the last four EWs, while an increase in SARS-CoV-2 circulation has been observed. In the United States, influenza activity has remained above the epidemic threshold with a slight increase in the last four EWs, RSV activity has decreased to moderate levels. Although SARS-CoV-2 has remained at high levels, it has shown a decreasing trend. Hospitalization rates for influenza, RSV, and SARS-CoV-2, after reaching similar high levels to the previous season, have shown a downward trend in the last four EWs. Caribbean ILI cases have shown an increase in the last four weeks associated with an increase in positive influenza and SARS-CoV-2 cases, while SARI cases have remained on the decline. Influenza activity has decreased in the last four EWs, reaching low circulation levels. During the last four EWs, the predominant viruses have been type A(H1N1)pdm09, followed by A(H3N2) and, to a lesser extent, B/Victoria. RSV activity has remained at low levels. SARS-CoV-2 activity has remained at high levels, although showing a decreasing trend. By countries Elevated influenza activity has been observed in Belize and Suriname. Elevated SARS-CoV-2 activity has been observed in Belize, Dominica, Jamaica, The Cayman Islands, and Guyana. Central America After an increase observed in previous weeks, ILI cases have decreased in the last four weeks, with most positive cases attributable to SARS-CoV-2 and, to a lesser extent, influenza. SARI cases have also shown a decrease, reaching low levels. After the increase observed in previous weeks, influenza activity has decreased in the last four EWs, reaching low levels. During this period, the predominant viruses have been type A(H1N1)pdm09, followed by B/Victoria and, to a lesser extent, A(H3N2). RSV activity has decreased to low levels. SARS-CoV-2 activity has decreased to low levels as well. By countries In El Salvador, SARS-CoV-2 activity has declined in the last four EWs after an initial increase over the preceding four EWs. In Guatemala, an increase in ILI cases associated with influenza was observed in late January 2024, with a steady decline in the number of reported ILI cases in the last three EWs, reaching moderate activity levels, while SARI cases have remained declining at epidemic levels. In Honduras, after the increase in ILI and SARI cases associated with positive influenza and SARS-CoV-2 cases observed in previous weeks, a decrease has been detected in the last three EWs, reaching levels below the epidemic threshold. In Nicaragua, RSV activity has increased slightly in the past EW after declining over the prior four EWs; both influenza and SARS-CoV-2 levels have remained low. After reaching high levels in early January 2024 in Panama, SARS-CoV-2 activity has decreased. However, after fluctuating around the epidemic threshold in the last four EWs, influenza activity levels rose sharply in the most recent EW. ILI and SARI cases, have steadily declined in the last four EWs, with the majority of positive cases attributable to SARS-CoV-2. Andean ILI activity has remained stable at low levels, and SARI cases, have increased in recent weeks with the highest proportion of positive cases attributable to SARS-CoV-2. Influenza activity has remained at low levels in the last four EWs. During this period, the predominant influenza viruses have been type A(H1N1)pdm09, with circulation of A(H3N2) and B/Victoria to a lesser extent. RSV activity has remained at low levels. SARS-CoV-2 activity has declined over the past four EWs. By countries In Bolivia, influenza circulation has increased in the most recent EW with influenza A(H3N2) dominating. SARI and ILI numbers have, however, remained low. In Colombia, SARS-CoV-2 activity have declined after an initial increase in mid-January 2024. SARI cases, after the increase associated with positive influenza and SARS-CoV-2 cases, have experienced a decrease in the last four EWs. In Ecuador, SARS-CoV-2 has remained stable at moderate levels of circulation; influenza activity has declined and has remained below the epidemic threshold for the past four weeks, and RSV activity has remained stable at high levels. SARI cases have increased in the most recent EW, associated with increased SARS-CoV-2 positivity. In Peru, SARS-CoV-2 activity has steadily declined over the past four EWs. Influenza activity in Venezuela has remained fluctuating below the epidemic threshold over the past four EWs with A(H1N1)pdm09, influenza A(H3N2), and influenza B/Victoria each contributing almost equally. Brazil and the Southern Cone SARI and ILI activity has remained low in the last four EWs, with most positive cases attributable to SARS-CoV-2. Influenza activity has remained at low circulation levels during the last four EWs. During this period, the predominant influenza viruses have been type A(H3N2) and A(H1N1)pdm09, followed by B/Victoria. RSV activity has remained at low levels. SARSCoV- 2 positivity has remained at high levels. By countries In Argentina, ILI and SARI levels have remained below the epidemic threshold. However, SARS-CoV-2 activity has persisted at elevated levels over the past four epidemiological weeks. In Brazil, SARS-CoV-2 activity has increased in the past two EWs, remaining at high levels. In Chile, after a marked decrease, SARS-CoV-2 activity has recently increased again in the last four EWs, with ILI cases remaining above the epidemic threshold, and, SARI cases below the epidemic threshold, mostly attributable to SARS-CoV-2 and, to a lesser extent, influenza. In Paraguay, SARS-CoV-2 circulation has shown a decrease in the last four EWs, reaching low levels, and influenza activity has decreased to levels below the epidemic threshold, SARI and ILI activity has been below epidemic levels, with most positive cases attributable to SARS-CoV-2. In Uruguay, SARI activity has continued at levels below the epidemic threshold, with most of the few positive cases attributable to SARS-CoV-2.