Regional Update, Influenza and Other Respiratory Viruses. Epidemiological Week 2 (19 January 2024)

ABSTRACT

[WEEKLY SUMMARY]. Regional Situation Regional Situation Over the last four Epidemiological Weeks (EWs), an increase in the activity of Influenza- Like Illness (ILI) has been observed in the Americas region, reaching elevated levels. Simultaneously, there has been a moderate and stable activity of Severe Acute Respiratory Infection (SARI), associated with positive cases of influenza and SARS-CoV-2. However, a decline was noted in the first two Epidemiological Weeks of the year, linked to underreporting. The rise in ILI activity is mainly linked to increases in North America and Central America, while SARI activity has only increased in North America. Regarding the circulation of respiratory viruses, a moderate activity of SARS-CoV-2 has been observed at the regional level compared to previous epidemic waves. Additionally, there has been an increase in influenza activity, reaching elevated levels considered epidemic for this time of the year. Moderate Respiratory Syncytial Virus (RSV) activity has remained stable. North America Influenza activity has remained at epidemic levels, showing a slight decrease. Over the last four EWs, 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 plateaued in the last four EWs with elevated circulation levels. SARS-CoV-2 activity continues at moderate levels, with a slight decrease in the last four EWs. ILI cases have continued to rise, with the majority attributable to influenza, though showing a decrease in this proportion. SARI cases have shown a slight decrease, with the majority attributable to influenza, and also showing a decrease in this proportion. By countries In Canada, SARS-CoV-2 activity has remained high in the last four EWs, although showing a decreasing trend. Influenza activity has continued to rise above the epidemic threshold, and RSV activity has remained stable at high levels during this period. In Mexico, influenza circulation has remained stable at epidemic levels in the last four EWs, with a decline in the last two EWs. SARI activity has shown a decline to epidemic levels, with the majority of positive cases being influenza in this period. In the United States, over the last four EWs, a decrease in influenza activity has been observed, remaining above the epidemic threshold. RSV and SARS-CoV-2 activities have remained stable at elevated levels, with a slightly decreasing trend. Hospitalization rates for influenza, RSV, and SARS-CoV-2, after reaching similar elevated levels to the previous season, have shown a downward trend in the last two EWs. Caribbean Influenza activity has shown a pronounced increase over the last four EWs, reaching elevated circulation levels. During this period, predominant viruses have been of type A(H1N1)pdm09, followed by A(H3N2) and, to a lesser extent, B/Victoria. RSV activity has remained in decline to low levels over the last four EWs. SARS-CoV-2 activity has increased in the last four EWs, reaching elevated levels. ILI and SARI cases have remained in decline over the last four EWs, with a higher proportion of ILI and SARI cases associated with influenza. By countries Elevated influenza activity has been observed in Belize, the Dominican Republic, Barbados, the Cayman Islands, and Saint Vincent and the Grenadines. Elevated SARS-CoV-2 activity has been observed in Jamaica, Saint Lucia, Barbados, the Cayman Islands, Guyana, and Saint Vincent and the Grenadines. Central America Influenza activity has shown a decline over the last four EWs, reaching low levels. During this period, predominant viruses have been of type A(H1N1)pdm09, followed by A(H3N2), and to a lesser extent, B/Victoria. RSV activity has shown a decline to intermediate levels. SARS-CoV-2 activity, although remaining at low levels, has increased in the last four EWs. ILI cases have shown an increase in the last four weeks, with the majority of positive cases attributable to SARS-CoV-2. SARI cases have remained in decline, with a higher proportion of cases associated with SARS-CoV-2. By countries In El Salvador, during the last four EWs, RSV activity has decreased to low levels, and SARS-CoV-2 activity has shown an increase. In Guatemala, a slight increase has been observed in ILI cases associated with influenza and, to a lesser extent, SARSCoV- 2. Regarding SARI cases, a slight increase has also been observed, with positive cases attributable to both influenza and RSV. In Honduras, influenza activity is at epidemic levels, with ILI and SARI cases continuing to decline, and the majority of positive cases being attributable to influenza. In Nicaragua, RSV activity has remained fluctuating at elevated levels. In Panama, SARS-CoV-2 activity has shown a pronounced increase, and influenza activity has increased slightly to epidemic levels. ILI and SARI cases have increased in the last four EWs, with the majority of positive cases attributable to SARS-CoV-2. Central America Influenza activity has shown a decline over the last four EWs, reaching low levels. During this period, predominant viruses have been of type A(H1N1)pdm09, followed by A(H3N2), and to a lesser extent, B/Victoria. RSV activity has shown a decline to intermediate levels. SARS-CoV-2 activity, although remaining at low levels, has increased in the last four EWs. ILI cases have shown an increase in the last four weeks, with the majority of positive cases attributable to SARS-CoV-2. SARI cases have remained in decline, with a higher proportion of cases associated with SARS-CoV-2. By countries In El Salvador, during the last four EWs, RSV activity has decreased to low levels, and SARS-CoV-2 activity has shown an increase. In Guatemala, a slight increase has been observed in ILI cases associated with influenza and, to a lesser extent, SARSCoV- 2. Regarding SARI cases, a slight increase has also been observed, with positive cases attributable to both influenza and RSV. In Honduras, influenza activity is at epidemic levels, with ILI and SARI cases continuing to decline, and the majority of positive cases being attributable to influenza. In Nicaragua, RSV activity has remained fluctuating at elevated levels. In Panama, SARS-CoV-2 activity has shown a pronounced increase, and influenza activity has increased slightly to epidemic levels. ILI and SARI cases have increased in the last four EWs, with the majority of positive cases attributable to SARS-CoV-2. Andean Influenza activity has remained at low levels over the last four EWs. During this period, predominant influenza viruses have been of type A(H1N1)pdm09, with circulation to a lesser extent of B/Victoria and A(H3N2). RSV activity has remained at low levels. SARS-CoV-2 activity has remained on the rise during this period, reaching elevated levels. ILI activity has remained stable at low levels, while SARI cases have shown an increase associated with the rise in the proportion of positives for SARS-CoV-2, influenza, and to a lesser extent, RSV. By countries In Bolivia, SARS-CoV-2 circulation has remained elevated. In Colombia, SARS-CoV-2 activity has shown a pronounced increase, reaching intermediate levels, and SARI cases have increased associated with cases of influenza, SARS-CoV- 2, and RSV. In Ecuador, although SARS-CoV-2 remains at elevated levels, it has shown a decrease. Similarly, influenza activity has continued to decline at epidemic levels, and RSV activity has shown a slight increase in the last two EWs. This has been accompanied by an increase in SARI cases, with moderate levels, mostly positive for influenza and SARS-CoV-2, and to a lesser extent, RSV. In Venezuela, an increase in influenza and RSV activity has been observed. Brazil and the Southern Cone Influenza activity has remained at low circulation levels over the last four EWs. During this period, predominant influenza viruses have been of type A(H3N2) and A(H1N1)pdm09, followed by B/Victoria. RSV activity has remained at low levels. SARS-CoV-2 activity has remained on the rise at high levels. SARI and ILI activities have remained low over the last four EWs, with the majority of positive cases attributable to SARS-CoV-2, showing a pronounced increase in percentage. 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 intermediate-high levels in the last four EWs. In Brazil, SARSCoV- 2 activity has remained at elevated levels during this period, albeit with a decreasing trend. In Chile, very high SARS-CoV-2 activity has been maintained, with an increase in influenza activity above the epidemic threshold in the last four EWs. ILI cases are at epidemic levels, while SARI cases are below this threshold, mostly attributable to SARS-CoV-2 and to a lesser extent, influenza. In Paraguay, SARS-CoV-2 circulation has risen in the last four EWs to elevated levels, with SARI activity remaining in decline at epidemic levels, and the majority of positive cases for ILI and SARI attributable to SARS-CoV-2. In Uruguay, SARI activity has continued at levels below the epidemic threshold, with the majority of positive cases attributable to SARS-CoV-2.