Regional Update, Influenza and Other Respiratory Viruses. Epidemiological Week 6 (16 February 2024)

ABSTRACT

[WEEKLY SUMMARY]. Regional Situation Over the past four epidemiological weeks (EWs), intermediate levels of Influenza-Like Illness (ILI) activity have been observed in the Americas region. Simultaneously, there has been a decrease in Severe Acute Respiratory Infection (SARI) activity, 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 and elevated activity observed in the Caribbean, while SARI activity has been particularly influenced by activity detected in North America. Regarding the circulation of respiratory viruses, there has been an increase in SARS-CoV-2 activity at the regional level, which remains moderate compared to previous epidemic waves. Additionally, epidemic influenza activity has been observed for this time of year, with moderate activity of Respiratory Syncytial Virus (RSV) showing a decline in the last four EWs. North America ILI cases, after a slight decrease in previous EWs, have remained at medium-high levels, with the majority of cases attributable to influenza, although showing a corresponding decrease in this proportion. SARI cases have shown a decrease, with most cases attributable to influenza and, to a lesser extent, SARS-CoV-2. Influenza activity has remained at epidemic circulation levels after a slight decrease in previous EWs. During this period, the 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 shown a decline in the last four EWs, remaining at moderate levels. SARS-CoV-2 activity has decreased in the last four EWs to low levels compared to previous waves. 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 to intermediate levels compared to previous waves. In the United States, influenza activity has remained above the epidemic threshold with a slight increase in the last three EWs, 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 elevated levels to the previous season, have shown a downward trend in the last four EWs. ILI cases have remained stable at epidemic levels. 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, with the majority associated with SARS-CoV-2 followed by influenza. Influenza activity has decreased in the last four EWs, reaching low circulation levels. During the last four EWs, the predominant viruses have been A(H1N1)pdm09, with concurrent circulation to a lesser extent of influenza A(H3N2) and B/Victoria. RSV activity has remained low. SARS-CoV-2 activity has remained at high levels, although showing a decreasing trend. By countries Increased influenza activity has been observed in Jamaica and Suriname. Elevated SARS-CoV-2 activity has been observed in Belize, Dominica, Haiti, Jamaica, the Cayman Islands, and Guyana. Central America Following the increase observed in previous weeks in ILI cases associated with positive cases of SARS-CoV-2, ILI activity has shown a decrease in the last four weeks, with the majority of positive cases attributable to SARS-CoV-2 and influenza. SARI cases have also shown a decrease, reaching low levels, with the majority of positive cases attributable to influenza and SARS-CoV-2. Influenza activity has decreased in the last four EWs, reaching low levels. During this period, the 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 has decreased in the last four EWs to low levels. By countries In El Salvador, SARS-CoV-2 activity remains at moderate levels. In Guatemala, an increase in ILI cases associated with influenza and to a lesser extent SARS-CoV-2 has been observed, reaching moderate levels of activity, while SARI cases have remained in decline at epidemic levels. In Honduras, following the increase in ILI and SARI cases associated with positive cases of influenza observed in previous weeks, a decrease has been detected in the last four EWs, reaching levels below the epidemic threshold. In Nicaragua, RSV activity has shown a decrease to low levels in the last four weeks, and both influenza and SARS-CoV-2 levels have remained low. In Panama, SARS-CoV-2 activity, after reaching high levels, has shown a decrease to low levels in the last four EWs. ILI and SARI cases, following the increase observed in previous EWs, have shown a decrease 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, after an increase, have shown a decrease with the highest proportion of positive cases attributable to SARS-CoV-2. Influenza activity has remained low in the last four EWs. During this period, the predominant influenza viruses have been A(H1N1)pdm09, with circulation to a lesser extent of B/Victoria and A(H3N2). RSV activity has remained low. SARS-CoV-2 activity has remained at high levels and on the rise. By countries In Bolivia, SARS-CoV-2 circulation has shown a marked decrease in the last EW to medium levels, with SARI activity below the epidemic threshold. In Colombia, SARS-CoV-2 activity has shown a pronounced increase in the last four EWs, reaching high levels; SARI cases, after the recent increase associated with positive cases of influenza and SARS-CoV-2, have experienced a decrease in the last two EWs, and deaths among SARI cases positive for SARS-CoV-2 have increased in the last two EWs. In Ecuador, SARS-CoV-2 has shown a decrease in activity to medium-low levels, influenza activity has continued to decline below the epidemic threshold, and RSV activity has shown a slight increase in the last four EWs. Following the recent increase in SARI cases associated with positive cases of influenza, SARS-CoV-2, and to a lesser extent RSV, a decrease in activity has been observed in the last four EWs, maintaining epidemic levels. In Venezuela, fluctuating influenza activity below the epidemic threshold has been observed in the last four EWs. Brazil and Southern Cone SARI and ILI activity have remained on a decreasing trend in the last four EWs, with the majority of positive cases attributable to SARS-CoV-2 with a rising percentage of positive cases. Influenza activity has remained at low circulation levels in the last four EWs. During this period, the 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, showing a slight increase in the last three EWs. Additionally, an increase in the positivity rate of SARS-CoV-2 has been observed, reaching high levels in the last four EWs. In Brazil, SARS-CoV-2 activity has remained on the rise at high levels. In Chile, following the marked decrease in SARS-CoV-2 activity recently experienced, an increase has been observed again in the last four EWs, with ILI cases at epidemic levels and SARI cases below this threshold, mostly attributable to SARS-CoV-2 and to a lesser extent influenza, whose activity has exceeded the epidemic threshold. In Paraguay, SARS-CoV-2 circulation has shown a decrease in the last four EWs, reaching moderate levels, and influenza activity has decreased to levels below the epidemic threshold. SARI activity has remained at epidemic levels with a downward trend, and the majority of positive cases are attributable to SARS-CoV-2. In Uruguay, SARI activity has continued at levels below the epidemic threshold, with a slight increase in the last four weeks, with the majority of the few positive cases attributable to SARS-CoV-2.