Regional Update, Influenza and Other Respiratory Viruses. Epidemiological Week 12 (29 March 2024)

[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, with a decreasing trend, primarily associated with moderate activity in North America and the Caribbean. Additionally, a decrease in Severe Acute Respiratory Infection (SARI) activity has been noted, currently at low levels. In both cases, the observed activity has been linked to positive cases of influenza and SARS-CoV-2. Regarding the circulation of respiratory viruses regionally, after an increase observed in previous weeks, SARS-CoV-2 activity has decreased, remaining moderate compared to previous epidemic waves. Influenza activity has remained at epidemic levels, while Respiratory Syncytial Virus (RSV) activity has declined and is currently at low levels. North America: Cases of ILI have decreased over the past four EWs, with intermediate levels, and the majority of cases attributed to influenza. Cases of SARI and hospitalizations associated with respiratory viruses have continued to decline. Influenza activity has remained at epidemic circulation levels, showing a slight decrease over the past four EWs. During this period, predominant influenza viruses have been type A, with concurrent circulation of influenza A(H1N1)pdm09 and influenza A(H3N2), and to a lesser extent, influenza B/Victoria. RSV activity has decreased over the past four EWs, remaining at intermediate-low levels. SARS-CoV-2 activity has decreased over the past four EWs to low levels compared to previous waves. By country: In Canada, SARS-CoV-2 activity has sharply decreased over the past four EWs to low levels. Influenza activity has remained at epidemic levels with a gradual decline, and RSV activity has also decreased to medium-low levels. In Mexico, influenza circulation has remained fluctuating at epidemic levels over the past four EWs, and SARS-CoV-2 circulation has remained at intermediate levels compared to previous waves. In the United States, influenza activity has shown a slight decrease over the past four EWs, although it remains above the epidemic threshold. Both RSV and SARS-CoV-2 have maintained a decreasing activity to low levels. ILI cases have shown a slight decrease and remain at intermediate levels. Hospitalization rates for influenza, RSV, and SARS-CoV-2, after reaching similar high levels as the previous season, have shown a decreasing trend over the past four EWs, reaching low levels. Caribbean: After the increase observed in previous EWs, ILI cases have shown a decrease in the past four EWs. SARI cases have continued to decline, with the majority of positive cases attributed to influenza. Influenza activity has decreased over the past four EWs, reaching low circulation levels. During the past four EWs, predominant viruses have been type A(H1N1)pdm09, with circulation to a lesser extent of influenza Type A(H3N2) and B/Victoria. RSV activity has remained at low levels. SARS-CoV-2 activity has remained in decline to low levels. By country: Elevated influenza activity has been observed in Jamaica, Suriname, and the Cayman Islands. Elevated SARS-CoV-2 activity has been observed in Saint Lucia and Guyana. Central America: ILI and SARI activity have remained stable at low levels over the past four EWs, with the majority of positive cases attributed to influenza. Influenza activity has shown a slight increase during this period, reaching intermediate-low levels. Over the past four EWs, predominant influenza viruses have been type A(H1N1)pdm09 with concurrent circulation of A(H3N2) and, to a lesser extent, B/Victoria. RSV and SARS-CoV-2 activity have remained at low levels. By country: In El Salvador, SARS-CoV-2 activity has decreased over the past four EWs to low levels, and influenza activity has fluctuated around the epidemic threshold. SARI activity, in turn, is around epidemic levels. In Guatemala, an increase in influenza-associated ILI cases has been observed, reaching moderate activity levels; SARI cases have remained at epidemic levels, mostly associated with influenza. In Honduras, an increase in SARI cases has been observed, reaching epidemic levels, associated with an increase in positive influenza cases, In Nicaragua, activity for RSV, influenza, and SARS-CoV-2 has decreased to low levels. In Panama, influenza activity has remained at epidemic levels over the past four EWs, and ILI and SARI cases have shown a slight increase. cases have continued to decline to low levels, with most positive cases attributed to SARS-CoV-2 and influenza. Influenza activity has remained at low levels over the past four EWs with a slightly increasing trend. During this period, predominant influenza viruses have been type A(H1N1)pdm09 with concurrent circulation of A(H3N2) and, to a lesser extent, B/Victoria. RSV activity has remained at low levels, albeit with a slight increase. SARS-CoV-2 activity has remained in decline at low levels. By country: In Bolivia, there has been an increase in ILI and SARI cases associated with positive influenza cases, with SARI levels around the epidemic threshold. Influenza activity has shown a marked increase, surpassing the elevated threshold. In Colombia, SARS-CoV-2 activity has decreased over the past four EWs to medium-low levels, while influenza and RSV activity have shown a slight increase. SARI activity has remained in decline around the epidemic threshold during these last four EWs, with positive cases attributed to influenza and RSV and, to a lesser extent, SARS-CoV-2. In Ecuador, SARS-CoV-2 remains at medium-high levels, influenza activity has remained below the epidemic threshold, and RSV activity continues at moderate levels. SARI activity has fluctuated around the moderate threshold, with positive SARI cases attributed to influenza, SARS-CoV- 2, and, to a lesser extent, RSV. In Venezuela, over the past four EWs, fluctuating influenza activity has been observed below the epidemic threshold. Brazil and the Southern Cone: ILI and SARI activity have shown a slight increase over the past four EWs, with the majority of positive cases attributed to SARS-CoV-2 and, to a lesser extent, influenza. Influenza activity has increased over the past four EWs, reaching epidemic threshold levels in some countries. During this period, predominant influenza viruses have been type A(H3N2), followed by A(H1N1)pdm09. RSV activity has remained at low levels. SARS-CoV-2 activity has remained in decline at intermediate activity levels. By country: In Argentina, ILI and SARI levels have remained below the epidemic threshold. The positivity rate for SARS-CoV-2, although remaining at moderate levels, has shown a marked decrease over the past four EWs, and influenza activity is below the epidemic threshold. In Brazil, SARS-CoV-2 activity continues to decline, with medium levels, and influenza activity has shown an increase over the past four EWs, reaching the epidemic threshold. In Chile, an increase in SARS-CoV-2 activity has been observed over the past four EWs, with moderate levels, a slight increase in influenza activity, surpassing the epidemic threshold has been observed. ILI cases have shown a pronounced increase to epidemic levels; SARI cases have slightly exceeded the epidemic threshold, with the majority of positive cases for both ILI and SARI attributed to SARS-CoV-2 and, to a lesser extent, influenza. In Paraguay, SARS-CoV-2 circulation has shown a decrease over the past four EWs, reaching low levels, and influenza and RSV activities have remained low. ILI and SARI activities have remained below the epidemic threshold, albeit with a slight increase. In Uruguay, SARI activity has continued to be below the epidemic threshold, although with a slight increase over the past four weeks, and the majority of positive cases attributed to SARS-CoV-2, which remains at moderate levels.