Regional Update, Influenza and Other Respiratory Viruses. Epidemiological Week 8 (1 March 2024)

ABSTRACT

[WEEKLY SUMMARY]. Regional Situation Over the past four Epidemiological Weeks (EWs), there has been a decline in lnfluenza-Like lllness (ILI) activity in the Americas region, stabilizing at medium levels. Similarly, a decrease has been observed in the activity of Severe Acute Respiratory lnfection (SARI), currently at low leveis. ln 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 decrease 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 epidemie waves. Influenza activity has decreased over the period; respiratory syncytial virus (RSV) activity, while remaining moderate, has also declined. North America ILI cases 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 epidemie levels after a slight decrease in recent EWs. During this period, the predominant influenza viruses have been type A(H 1 N 1)pdm09, with concurrent circulation of influenza A(H3N2) and, to a lesser extent, influenza B/Victoria. RSV activity has declined in the last four EWs, remaining at moderate levels. SARS-CoV-2 positivity has decreased in the last four EWs and remains below late 2023 levels. By countries ln Canada, SARS-CoV-2 activity has markedly decreased in the last four EWs to medium leveis. Influenza activity remains at epidemie levels, and RSV activity has declined during this period. ln Mexico, influenza circulation has remained fluctuating at epidemie levels in the last four EWs, while an increase in SARS-CoV-2 circulation has been observed. ln the United States, influenza activity has decreased in the past four EWS and remained above the epidemie threshold, RSV activity has decreased to moderate levels, and 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 declined from high levels in preceding weeks to moderate levels in the most recent EW associated with decreases in positive influenza and SARS-Co-V-2 cases; SARI cases have remained on the decline. Influenza activity has increased in the last four EWs, reaching low circulation levels. During the last four EWs, the predominant viruses have been type A(H1 N1)pdm09, followed by A(H3N2) and, to a lesser extent, B/Victoria. RSV activity has remained at low levels. SARS-CoV-2 activity has declined to moderate levels, continuing to show a decreasing trend. By countries Elevated influenza activity has been observed in Suriname. Central America ILI and SARI cases have decreased in the last four weeks, with the majority of positive cases attributable to SARSCoV- 2 and, to a lesser extent, influenza. Influenza activity has decreased in the last four EWs, with an increase noted in the most recent EW, however remaining at low levels. During this period, the predominant viruses have been type A(H1 N1)pdm09, followed by A(H3N2) and B/Victoria. RSV activity has decreased to low levels. SARS-CoV-2 activity further declined and remained at low levels. By countries ln EI Salvador, SARS-CoV-2 activity continued to decline over the past four EWs. ln Guatemala, ILI cases were sustained at high levels and SARI cases while declining to moderate levels showed increasing positivity for SARS-Co-V-2 and influenza. ln Honduras, both ILI and SARI cases increased slightly in the past four EWs, however both remain below epidemie levels. Influenza activity continued at epidemie leveis. ln Nicaragua, RSV activity has continued to decline; 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 epidemie threshold in the last four EWs, influenza activity levels have increased to epidemie levels. ILI and SARI cases, have declined in the last four EWs. Andean ILI activity has remained stable at iow levels, and SARI casesremaineda t high levels, with the highest proportion of positive cases attributable to SARS-CoV-2. Influenza activity has remained at low leveis in the last four EWs. During this period, the predominant influenza viruses have been type A(H1 N1)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 ln Bolivia, influenza circulation has increased in recent EWs with influenza A(H3N2) dominating. SARI and ILI numbers have, however, remained low. ln Colombia, SARS-CoV-2 activity have declined after an initial increase in mid-January 2024. ln Ecuador, SARS-CoV-2 has shown an increase in activity in the past EW; influenza activity has continued to decline and has remained beneath epidemie thresholds for the past four EWs, and RSV activity has declined. SARI cases have also decreased. ln Peru, SARSCoV- 2 activity has steadily declined over the past four EWs. Influenza activity in Venezuela has increased over the past four EWs with A(H1N1)pdm09 dominating followed by influenza A(H3N2), and influenza B/Victoria. Brazil and the Southem 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 circuiation levels during the last four EWs, with a slight increase in the last two 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. SARS-CoV-2 positivity has remained at high levels, however the number of positives has declined. By countries ln Argentina, ILI and SARI levels have remained below the epidemie threshold. After an initial inerease in the positivity rate of SARS-CoV-2 in late January, a decline has been observed, remaining at high ievels. ln Brazil, SARS-CoV-2 activity has increased in the past four EWs, remaining at high levels. ln Chile, after a marked deerease, SARS-CoV-2 activity has reeently increased again in the last four EWs, with ILI cases remaining above epidemie levels, however, SARI cases remained just below the epidemie threshold, mostly attributable to SARS-CoV-2. ln Paraguay, SARS-CoV-2 cireulation has shown a decrease in the last three EWs, reaching moderate leveis, and influenza aetivity has increased above the epidemie threshold, while SARI activity has been below epidemie leveis, with most positive cases attributable to SARS-CoV-2. ln Uruguay, SARI activity has continued at levels below the epidemie threshold, with most of the few positive cases attributable to SARS-CoV-2.