Regional Update, Influenza and Other Respiratory Viruses. Epidemiological Week 18 (10 May 2024)

[WEEKLY SUMMARY]. Regional Situation: Over the past four epidemiological weeks (EWs), low activity levels of Influenza-Like Illness (ILI) have been noted across the Americas, exhibiting a declining trend primarily linked to North America. Simultaneously, there has been a reduction in Severe Acute Respiratory Infection (SARI) activity, which also remains low. These trends are largely associated with confirmed cases of influenza and, to a lesser extent, SARS-CoV-2. Regionally, SARS-CoV-2 activity has decreased to low levels compared to previous epidemic waves. Moreover, there has been a slight decline in seasonal influenza activity and a decrease in Respiratory Syncytial Virus (RSV) activity, both of which are currently low. North America: Over the last four EWs, ILI cases have continued to decline, predominantly due to influenza, resulting in intermediate-low activity levels. Hospitalizations due to respiratory viruses have also followed a downward trend, remaining low. While influenza has maintained epidemic circulation levels, there has been a notable decrease during this period. The most common influenza viruses have been type B/Victoria, with lesser circulation of influenza A(H3N2) and A(H1N1)pdm09. RSV activity has similarly decreased, stabilizing at low levels. SARS-CoV-2 activity has remained at low levels. By country: Canada SARS-CoV-2 activity has remained at low levels over the last four EWs. Influenza activity has sustained epidemic levels but has gradually decreased, and RSV activity has continued to decline, remaining low. In Mexico, influenza circulation has stayed fluctuating at epidemic levels, while SARS-CoV-2 activity has decreased to low levels. In the United States, influenza activity has decreased over the last four EWs but remains above the epidemic threshold. Both RSV and SARSCoV- 2 activities have continued their decline to low levels. ILI cases have decreased and are now at intermediate-low levels. Hospitalization rates for influenza, RSV, and SARS-CoV-2 have followed a decreasing trend, maintaining low levels. Caribbean: ILI and SARI cases have maintained a downward trend over the last four weeks, primarily involving influenza and, to a lesser extent, SARS-CoV-2. Influenza activity has been low but fluctuating during the last four EWs. The predominant viruses have been type A(H3N2), with concurrent circulation of influenza A(H1N1)pdm09 and to a lesser extent, B/Victoria. Both RSV and SARS-CoV-2 activities have remained low. By country: Influenza activity was noted in Belize, Jamaica, Guyana, and the Cayman Islands, while SARS-CoV-2 activity was observed in Barbados, Guyana, and Trinidad and Tobago. Central America: Over the last four epidemiological weeks (EWs), both ILI and SARI cases have maintained low activity levels, though with a slight increase, predominantly attributed to influenza cases. During this period, influenza activity has seen a slight rise, remaining at intermediate-low levels. The most prevalent influenza viruses have been type A(H3N2) along with concurrent circulation of A(H1N1)pdm09. Both Respiratory Syncytial Virus (RSV) and SARS-CoV-2 have consistently exhibited low levels of activity. By country: In El Salvador, SARI activity has been around epidemic levels, with SARS-CoV-2 maintaining low circulation and influenza activity fluctuating near the epidemic threshold. Guatemala has experienced stable ILI and SARI activities at epidemic levels throughout the last four EWs, associated with influenza cases at moderate circulation levels. Honduras has seen variable SARI activity around epidemic levels, connected to declining influenza cases at similar levels. In Nicaragua, RSV, influenza, and SARS-CoV-2 activities have all been low. Panama has reported an uptick in both ILI and SARI cases during this period, with influenza activity reaching epidemic levels. Andean Region: ILI activity has remained consistently low across the last four EWs. SARI cases have also been stable at low levels, although there has been a notable increase in RSV-positive cases and, to a lesser extent, influenza. The influenza activity has been low but fluctuating throughout this period, with type A(H3N2) and A(H1N1)pdm09 being the predominant viruses. RSV activity, while still low, has been on an upward trend. SARS-CoV-2 activity has continued to decline, maintaining low levels. By country: In Colombia, RSV, despite being at low levels, has shown an upward trend over the last four EWs, while SARS-CoV- 2 activity has decreased, staying at low levels, with influenza activity slightly increasing but remaining below the epidemic threshold. SARI activity has fluctuated around the epidemic threshold, primarily involving cases attributable to RSV and influenza. In Ecuador, following a significant increase in RSV activity in earlier EWs, there has been a reduction to medium levels; SARS-CoV-2 has also decreased to low levels, and influenza activity has exceeded the epidemic threshold. SARI activity in Ecuador is at epidemic levels, with most cases predominantly due to RSV and, to a lesser extent, influenza. In Peru, influenza activity has oscillated around the epidemic threshold, and SARS-CoV-2 activity has dropped to low levels. In Venezuela, influenza activity has been variable but generally around the epidemic threshold over the last four EWs. Brazil and the Southern Cone: In the last four EWs, there has been an increase in both ILI and SARI activities, achieving intermediate levels, with the majority of cases attributed to influenza. During this period, influenza activity has escalated to epidemic levels in most of these countries. The primary influenza viruses have been type A(H3N2) and, less frequently, A(H1N1)pdm09. RSV activity has remained low, though it has slightly increased. SARS-CoV-2 activity has persistently declined, staying at low levels. By country: In Argentina, both ILI and SARI levels have stayed below the epidemic threshold. However, influenza activity has risen above these levels, while SARS-CoV-2 positivity rates continue to decline, reaching low levels with a slight uptick in RSV positivity observed. In Brazil, SARS-CoV-2 activity has maintained low levels, and influenza activity remains below the epidemic threshold. In Chile, the last four EWs have seen a significant increase in both ILI and SARI cases, achieving extraordinary and epidemic levels respectively, predominantly driven by high levels of influenza activity. In Paraguay, SARI activity has crossed the epidemic threshold, though ILI activity continues to stay below it. Influenza activity is around the epidemic threshold, with the circulation of SARS-CoV-2 and RSV maintaining stable low levels. In Uruguay, SARI activity has exceeded the epidemic threshold, largely due to SARS-CoV-2 and influenza, both of which have also surpassed the epidemic levels.