Regional Update, Influenza and Other Respiratory Viruses. Epidemiological Week 3 (26 January 2024)

ABSTRACT

[WEEKLY SUMMARY]. Regional Situation Over the past four epidemiological weeks (EWs), a decline in the activity of Influenza-Like Illness (ILI) has been observed in the Americas region, reaching intermediate levels. Additionally, there is a moderate-to-low and decreasing activity of Severe Acute Respiratory Infection (SARI), associated with positive cases of influenza and SARS-CoV-2. The moderate ILI activity has been mainly linked to North America and the Caribbean, currently on the decline, while SARI activity has been particularly influenced by the observed activity in North America. Concerning the circulation of respiratory viruses, a moderate level of SARS-CoV-2 activity has been maintained at the regional level compared to previous epidemic waves. Likewise, there has been an observed epidemic level of influenza activity for this time of the year with a slight decrease, along with a stably moderate activity of Respiratory Syncytial Virus (RSV). North America Cases of ILI have significantly decreased, with most cases attributable to influenza, although there is also a decline in this proportion. Similarly, SARI cases have shown a decrease, with most cases attributable to influenza and to a lesser extent to SARSCoV-2. Influenza activity has remained epidemic, showing a decrease in the last four EWs. During this period, predominant influenza viruses have been A(H1N1)pdm09, with concurrent circulation of influenza B/Victoria, and to a lesser extent, influenza A(H3N2). RSV activity has slightly decreased in the last EW, maintaining moderate levels. SARS-CoV-2 activity continues at moderate levels, showing a decrease in the last four EWs. By country In Canada, SARS-CoV-2 activity has remained high in the last four EWs, albeit showing a decreasing trend. Influenza activity has also decreased but remains above the epidemic threshold, while RSV activity has remained stable at high levels during this period. In Mexico, influenza circulation has fluctuated at epidemic levels in the last four EWs, and a slight increase in SARS-CoV-2 circulation has been observed. SARI activity has decreased to epidemic levels, with the majority of positive cases being influenza during this period. In the United States, influenza activity has remained stable above the epidemic threshold, and although RSV and SARS-CoV-2 activities have remained at high levels, they have shown a slight decreasing trend. Hospitalization rates for influenza, RSV, and SARS-CoV-2, after reaching similar high levels as the previous season, have shown a downward trend in the last three EWs. Caribbean ILI cases have shown an increase in the last four weeks associated with an increase in positive cases of influenza, while SARI cases have remained in decline. Influenza activity has decreased in the last two EWs, reaching intermediate circulation levels. During this period, predominant viruses have been A(H1N1)pdm09, followed by A(H3N2), and to a lesser extent, B/Victoria. RSV activity has remained low. SARS-CoV-2 activity has increased in the last four EWs, reaching high levels. By countries Elevated influenza activity has been observed in the Dominican Republic, Jamaica, the Cayman Islands, Guyana, and Saint Vincent and the Grenadines. Elevated SARS-CoV-2 activity has been observed in Belize, Dominica, Jamaica, Saint Lucia, Barbados, the Cayman Islands, Guyana, and Saint Vincent and the Grenadines. Central America ILI cases have shown an increase in the last four weeks, with the majority of positive cases attributable to SARS-CoV2. SARI cases have shown a slight increase, with a slight rise in the proportion of positive cases for SARS-CoV-2. Influenza activity has increased in the last three EWs, reaching moderate levels. During this period, predominant viruses have been 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, although remaining at low levels, has shown an increase in the last four EWs. By countries In El Salvador, SARS-CoV-2 activity has shown a marked increase in the last two EWs, reaching intermediate levels. In Guatemala, an increase in ILI cases associated with influenza and, to a lesser extent, SARS-CoV-2 has been observed, reaching epidemic activity levels. Regarding SARI cases, there has also been a slight increase with positive cases attributable to both influenza and RSV, reaching epidemic levels. In Honduras, a slight increase has been observed in both ILI and SARI cases associated with positive cases of influenza, with activity at epidemic levels. In Nicaragua, RSV activity has shown a decrease to low levels in the last three weeks. In Panama, SARS-CoV-2 activity has shown a pronounced increase, and influenza activity has slightly increased to epidemic levels. Both ILI and SARI cases have increased 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, while SARI cases have shown an increase associated with an increase in the proportion of positives for SARS-CoV-2, influenza, and to a lesser extent, RSV. Influenza activity has remained low in the last four EWs. During this period, predominant influenza viruses have been A(H1N1)pdm09, with lesser circulation of B/Victoria and A(H3N2). RSV activity has remained low. SARS-CoV-2 activity has remained at high levels. By countries In Bolivia, SARS-CoV-2 circulation has remained high. In Colombia, SARS-CoV-2 activity has shown a pronounced increase, reaching medium-high levels in the last four EWs. SARI cases have increased, associated with positive cases of influenza first, followed by SARS-CoV-2 and RSV. In Ecuador, although SARS-CoV-2 remains at high levels, it has shown a decrease. Similarly, influenza activity has continued to decrease at epidemic levels, and RSV activity has shown a slight increase in the last three EWs. This has been accompanied by an increase in SARI cases in the last four EWs, reaching epidemic levels in the last EW, with the majority of positive cases being influenza and SARS-CoV-2 and, to a lesser extent, RSV. In Venezuela, an increase has been observed in influenza and RSV activity. Brazil and the Southern Cone SARI and ILI activity has remained low in the last four EWs, with the majority of positive cases attributable to SARS-CoV-2 and a pronounced increase in the percentage of positive cases. Influenza activity has remained at low circulation levels in the last four EWs. During this period, predominant influenza viruses have been A(H3N2) and A(H1N1)pdm09, followed by B/Victoria. RSV activity has remained low. SARS-CoV-2 activity has remained on the rise at high levels. By countries In Argentina, ILI and SARI levels have remained below the epidemic threshold. However, an increase in the percentage of SARS-CoV-2 positivity has been observed, reaching high levels in the last four EWs. In Brazil, SARS-CoV-2 activity has remained stable at high levels during this period. In Chile, SARS-CoV-2 activity has remained very high, with ILI cases at epidemic levels and SARI cases below this threshold, mostly attributable to SARS-CoV-2 and, to a lesser extent, influenza. In Paraguay, SARS-CoV-2 circulation has increased in the last four EWs, reaching high levels, and influenza activity has increased to epidemic levels. SARI activity has remained at epidemic levels, with the majority of positive cases attributable to SARS-CoV-2 and, to a lesser extent, influenza. In Uruguay, SARI activity has continued below the epidemic threshold, with the majority of scarce positive cases attributable to SARS-CoV-2.