Public health and economic benefits of seasonal influenza vaccination in risk groups in France, Italy, Spain and the UK: state of play and perspectives.

BACKGROUND: Seasonal influenza epidemics have a substantial public health and economic burden, which can be alleviated through vaccination. The World Health Organization (WHO) recommends a 75% vaccination coverage rate (VCR) in: older adults (aged ≥ 65 years), individuals with chronic conditions, pregnant women, children aged 6-24 months and healthcare workers. However, no European country achieves this target in all risk groups. In this study, potential public health and economic benefits achieved by reaching 75% influenza VCR was estimated in risk groups across four European countries: France, Italy, Spain, and the UK. METHODS: A static epidemiological model was used to estimate the averted public health and economic burden of increasing the 2021/2022 season VCR to 75%, using the efficacy data of standard-dose quadrivalent influenza vaccine. For each country and risk group, the most recent data on population size, VCR, pre-pandemic influenza epidemiology, direct medical costs and absenteeism were identified through a systematic literature review, supplemented by manual searching. Outcomes were: averted influenza cases, general practitioner (GP) visits, hospitalisations, case fatalities, number of days of work lost, direct medical costs and absenteeism-related costs. RESULTS: As of the 2021/2022 season, the UK achieved the highest weighted VCR across risk groups (65%), followed by Spain (47%), France (44%) and Italy (44%). Based on modelling, the 2021/2022 VCR prevented an estimated 1.9 million influenza cases, avoiding 375,200 GP visits, 73,200 hospitalisations and 38,400 deaths. To achieve the WHO 75% VCR target, an additional 24 million at-risk individuals would need to be vaccinated, most of which being older adults and patients with chronic conditions. It was estimated that this could avoid a further 918,200 influenza cases, 332,000 GP visits, 16,300 hospitalisations and 6,300 deaths across the four countries, with older adults accounting for 52% of hospitalisations and 80% of deaths. An additional €84 million in direct medical costs and €79 million in absenteeism costs would be saved in total, with most economic benefits delivered in France. CONCLUSIONS: Older adults represent most vaccine-preventable influenza cases and deaths, followed by individuals with chronic conditions. Health authorities should prioritise vaccinating these populations for maximum public health and economic benefits.

Ozone as an environmental driver of influenza.

Under long-standing threat of seasonal influenza outbreaks, it remains imperative to understand the drivers of influenza dynamics which can guide mitigation measures. While the role of absolute humidity and temperature is extensively studied, the possibility of ambient ozone (O3) as an environmental driver of influenza has received scant attention. Here, using state-level data in the USA during 2010-2015, we examined such research hypothesis. For rigorous causal inference by evidence triangulation, we applied 3 distinct methods for data analysis: Convergent Cross Mapping from state-space reconstruction theory, Peter-Clark-momentary-conditional-independence plus as graphical modeling algorithms, and regression-based Generalised Linear Model. The negative impact of ambient O3 on influenza activity at 1-week lag is consistently demonstrated by those 3 methods. With O3 commonly known as air pollutant, the novel findings here on the inhibition effect of O3 on influenza activity warrant further investigations to inform environmental management and public health protection.

SARS-CoV-2 and influenza virus coinfections in the Tuscan population during the 2021/2022 influenza season.

Introduction: The 2021/2022 influenza season was not characterised by a well-defined incidence peak. As reported by the Italian National Institute of Health, a high value of incidence of influenza cases was recorded in week 13, but it was still lower than in other influenza seasons. This abnormal circulation was probably due to relaxation of the COVID-19 pandemic restriction measures, such as social distancing, smart-working, home leaning and the use of masks, which greatly reduced the circulation of respiratory-transmitted viruses, including human respiratory syncytial virus (HRSV). The symptoms of SARS-CoV-2 and influenza are quite similar, sharing the human-to-human transmission route via respiratory droplets. Methods: The aim of this study was to estimate the rate of coinfection with influenza viruses and/or HRSV in SARS-CoV-2-positive subjects (N = 940) in a population of central Italy during the 2021/2022 season. Results: A total of 54 cases of coinfection were detected during the study period, 51 cases (5.4%) of SARS-CoV-2 and influenza virus and three cases (0.3%) of SARS-CoV-2 and HRSV coinfection. Conclusions: These results highlight the importance of continuous monitoring of the circulation of influenza virus and other respiratory viruses in the context of the COVID-19 pandemic.

Characterizing the antigenic evolution of pandemic influenza A (H1N1) pdm09 from 2009 to 2023.

The H1N1pdm09 virus has been a persistent threat to public health since the 2009 pandemic. Particularly, since the relaxation of COVID-19 pandemic mitigation measures, the influenza virus and SARS-CoV-2 have been concurrently prevalent worldwide. To determine the antigenic evolution pattern of H1N1pdm09 and develop preventive countermeasures, we collected influenza sequence data and immunological data to establish a new antigenic evolution analysis framework. A machine learning model (XGBoost, accuracy = 0.86, area under the receiver operating characteristic curve = 0.89) was constructed using epitopes, physicochemical properties, receptor binding sites, and glycosylation sites as features to predict the antigenic similarity relationships between influenza strains. An antigenic correlation network was constructed, and the Markov clustering algorithm was used to identify antigenic clusters. Subsequently, the antigenic evolution pattern of H1N1pdm09 was analyzed at the global and regional scales across three continents. We found that H1N1pdm09 evolved into around five antigenic clusters between 2009 and 2023 and that their antigenic evolution trajectories were characterized by cocirculation of multiple clusters, low-level persistence of former dominant clusters, and local heterogeneity of cluster circulations. Furthermore, compared with the seasonal H1N1 virus, the potential cluster-transition determining sites of H1N1pdm09 were restricted to epitopes Sa and Sb. This study demonstrated the effectiveness of machine learning methods for characterizing antigenic evolution of viruses, developed a specific model to rapidly identify H1N1pdm09 antigenic variants, and elucidated their evolutionary patterns. Our findings may provide valuable support for the implementation of effective surveillance strategies and targeted prevention efforts to mitigate the impact of H1N1pdm09.

Assessing the change in the epidemiology of seasonal respiratory viruses with the onset of the COVID-19 pandemic.

Background. Respiratory tract infections are among the most important causes of mortality and morbidity in children worldwide. The COVID-19 pandemic has affected the distribution of seasonal respiratory viruses as in all areas of life. In this study, we have aimed to evaluate the changes in the rates of seasonal respiratory viruses with the onset of the pandemic.Methods. This study included patients who were admitted to the Pediatrics Clinic of Eskisehir Osmangazi University Faculty of Medicine Hospital between December 2018 and February 2022 with respiratory tract infections and in whom pathogens were detected from nasopharyngeal swab samples analysed by multiplex PCR method.Results. A total of 833 respiratory tract pathogens were detected in 684 cases consisting of male (55.3 %), and female (44.7 %), patients with a total mean age of 42 months. Single pathogen was revealed in 550, and multiple pathogens in 134 cases. Intensive care was needed in 14 % of the cases. Most frequently influenza A/B, rhinovirus and respiratory syncytial virus (RSV) were detected during the pre-pandemic period, while rhinovirus, RSV, and adenovirus were observed during the lockdown period. In the post-lockdown period, the incidence rates of rhinovirus, RSV, human bocavirus (HboV) (12 %), influenza virus infections increased, and patients with RSV and bocavirus infections required intensive care hospitalization.Conclusion. It is thought that the COVID-9 pandemic lockdown measures may have an impact on the distribution of seasonal respiratory viruses, especially RSV and influenza. Current, prospective and large case series regarding the mechanism of action and dynamics are needed.

Seasonal antigenic prediction of influenza A H3N2 using machine learning.

Antigenic characterization of circulating influenza A virus (IAV) isolates is routinely assessed by using the hemagglutination inhibition (HI) assays for surveillance purposes. It is also used to determine the need for annual influenza vaccine updates as well as for pandemic preparedness. Performing antigenic characterization of IAV on a global scale is confronted with high costs, animal availability, and other practical challenges. Here we present a machine learning model that accurately predicts (normalized) outputs of HI assays involving circulating human IAV H3N2 viruses, using their hemagglutinin subunit 1 (HA1) sequences and associated metadata. Each season, the model learns an updated nonlinear mapping of genetic to antigenic changes using data from past seasons only. The model accurately distinguishes antigenic variants from non-variants and adaptively characterizes seasonal dynamics of HA1 sites having the strongest influence on antigenic change. Antigenic predictions produced by the model can aid influenza surveillance, public health management, and vaccine strain selection activities.

Molecular characterization of influenza virus circulating in Nepal in the year 2019.

Influenza (sometimes referred to as "flu") is a contagious viral infection of the airways in the lungs that affects a significant portion of the world's population. Clinical symptoms of influenza virus infections can range widely, from severe pneumonia to moderate or even asymptomatic sickness. If left untreated, influenza can have more severe effects on the heart, brain, and lungs than on the respiratory tract and can necessitate hospitalization. This study was aimed to investigate and characterize all types of influenza cases prevailing in Nepal and to analyze seasonal occurrence of Influenza in Nepal in the year 2019. A cross sectional, retrospective and descriptive study was carried out at National Influenza Center (NIC), National Public Health Laboratory Kathmandu Nepal for the period of one year (Jan-Dec 2019). A total of 3606 throat swab samples from various age groups and sexes were processed at the NIC. The specimens were primarily stored at 4 °C and processed using ABI 7500 RT PCR system for the identification of Influenza virus types and subtypes. Data accessed for research purpose were retrieved from National Influenza Centre (NIC) on 1st Jan 2020. Of the total 3606 patients suspected of having influenza infection, influenza viruses were isolated from 1213 (33.6%) patients with male predominance. The highest number of infection was caused by Influenza A/Pdm09 strain 739 (60.9%) followed by Influenza B 304 (25.1%) and Influenza A/H3 169 (13.9%) and most remarkable finding of this study was the detection of H5N1 in human which is the first ever case of such infection in human from Nepal. Similar to other tropical nations, influenza viruses were detected year-round in various geographical locations of Nepal. The influenza virus type and subtypes that were in circulation in Nepal were comparable to vaccine candidate viruses, which the currently available influenza vaccine may prevent.

Effectiveness of inactivated influenza vaccine against laboratory-confirmed influenza among Chinese elderly: a test-negative design.

BACKGROUND: Evidence on the effectiveness of influenza vaccination in the elderly is limited, and results are controversial. There are also few reports from China. METHODS: We conducted a test-negative case-control study design to estimate influenza vaccine effectiveness (VE) against laboratory-confirmed influenza-associated visits among elderly (aged ≥ 60 years) across four influenza seasons in Ningbo, China, from 2018 to 19 to 2021-22. Influenza-positive cases and negative controls were randomly matched in a 1:1 ratio according to age, sex, hospital, and date of influenza testing. We used logistic regression models to compare vaccination odds ratios (ORs) in cases to controls. We calculated the VE as [100% × (1-adjusted OR)] and calculated the 95% confidence interval (CI) around the estimate. RESULTS: A total of 30,630 elderly patients tested for influenza with virus nucleic acid or antigen during the study period. After exclusions, we included 1 825 influenza-positive cases and 1 825 influenza-negative controls. Overall, the adjusted VE for influenza-related visits was 63.5% (95% CI, 56.3-69.5%), but varied by season. Influenza VE was 59.8% (95% CI, 51.5-66.7%) for influenza A and 89.6% (95% CI, 77.1-95.3%) for influenza B. The VE for ages 60-69 and 70-79 was 65.2% (95% CI, 55.4-72.9%) and 69.8% (95% CI, 58.7-77.9%), respectively, but only 45.4% (95% CI, 6.2-68.2%) for ages 80 and over. CONCLUSIONS: Standard-dose inactivated influenza vaccine has shown good protection in the elderly in China. However, protection may not be satisfactory in people aged 80 years and older.

The Changing Landscape of Respiratory Viruses Contributing to Hospitalizations in Quebec, Canada: Results From an Active Hospital-Based Surveillance Study.

BACKGROUND: A comprehensive description of the combined effect of SARS-CoV-2 and respiratory viruses other than SARS-CoV-2 (ORVs) on acute respiratory infection (ARI) hospitalizations is lacking. OBJECTIVE: This study aimed to compare the viral etiology of ARI hospitalizations before the pandemic (8 prepandemic influenza seasons, 2012-13 to 2019-20) and during 3 pandemic years (periods of increased SARS-CoV-2 and ORV circulation in 2020-21, 2021-22, and 2022-23) from an active hospital-based surveillance network in Quebec, Canada. METHODS: We compared the detection of ORVs and SARS-CoV-2 during 3 pandemic years to that in 8 prepandemic influenza seasons among patients hospitalized with ARI who were tested systematically by the same multiplex polymerase chain reaction (PCR) assay during periods of intense respiratory virus (RV) circulation. The proportions of infections between prepandemic and pandemic years were compared by using appropriate statistical tests. RESULTS: During prepandemic influenza seasons, overall RV detection was 92.7% (1384/1493) (respiratory syncytial virus [RSV]: 721/1493, 48.3%; coinfections: 456/1493, 30.5%) in children (<18 years) and 62.8% (2723/4339) (influenza: 1742/4339, 40.1%; coinfections: 264/4339, 6.1%) in adults. Overall RV detection in children was lower during pandemic years but increased from 58.6% (17/29) in 2020-21 (all ORVs; coinfections: 7/29, 24.1%) to 90.3% (308/341) in 2021-22 (ORVs: 278/341, 82%; SARS-CoV-2: 30/341, 8.8%; coinfections: 110/341, 32.3%) and 88.9% (361/406) in 2022-23 (ORVs: 339/406, 84%; SARS-CoV-2: 22/406, 5.4%; coinfections: 128/406, 31.5%). In adults, overall RV detection was also lower during pandemic years but increased from 43.7% (333/762) in 2020-21 (ORVs: 26/762, 3.4%; SARS-CoV-2: 307/762, 40.3%; coinfections: 7/762, 0.9%) to 57.8% (731/1265) in 2021-22 (ORVs: 179/1265, 14.2%; SARS-CoV-2: 552/1265, 43.6%; coinfections: 42/1265, 3.3%) and 50.1% (746/1488) in 2022-23 (ORVs: 409/1488, 27.5%; SARS-CoV-2: 337/1488, 22.6%; coinfections: 36/1488, 2.4%). No influenza or RSV was detected in 2020-21; however, their detection increased in the 2 subsequent years but did not reach prepandemic levels. Compared to the prepandemic period, the peaks of RSV hospitalization shifted in 2021-22 (16 weeks earlier) and 2022-23 (15 weeks earlier). Moreover, the peaks of influenza hospitalization shifted in 2021-22 (17 weeks later) and 2022-23 (4 weeks earlier). Age distribution was different compared to the prepandemic period, especially during the first pandemic year. CONCLUSIONS: Significant shifts in viral etiology, seasonality, and age distribution of ARI hospitalizations occurred during the 3 pandemic years. Changes in age distribution observed in our study may reflect modifications in the landscape of circulating RVs and their contribution to ARI hospitalizations. During the pandemic period, SARS-CoV-2 had a low contribution to pediatric ARI hospitalizations, while it was the main contributor to adult ARI hospitalizations during the first 2 seasons and dropped below ORVs during the third pandemic season. Evolving RVs epidemiology underscores the need for increased scrutiny of ARI hospitalization etiology to inform tailored public health recommendations.

The antigenic landscape of human influenza N2 neuraminidases from 2009 until 2017.

Human H3N2 influenza viruses are subject to rapid antigenic evolution which translates into frequent updates of the composition of seasonal influenza vaccines. Despite these updates, the effectiveness of influenza vaccines against H3N2-associated disease is suboptimal. Seasonal influenza vaccines primarily induce hemagglutinin-specific antibody responses. However, antibodies directed against influenza neuraminidase (NA) also contribute to protection. Here, we analysed the antigenic diversity of a panel of N2 NAs derived from human H3N2 viruses that circulated between 2009 and 2017. The antigenic breadth of these NAs was determined based on the NA inhibition (NAI) of a broad panel of ferret and mouse immune sera that were raised by infection and recombinant N2 NA immunisation. This assessment allowed us to distinguish at least four antigenic groups in the N2 NAs derived from human H3N2 viruses that circulated between 2009 and 2017. Computational analysis further revealed that the amino acid residues in N2 NA that have a major impact on susceptibility to NAI by immune sera are in proximity of the catalytic site. Finally, a machine learning method was developed that allowed to accurately predict the impact of mutations that are present in our N2 NA panel on NAI. These findings have important implications for the renewed interest to develop improved influenza vaccines based on the inclusion of a protective NA antigen formulation.

Two proteins, the hemagglutinin and the neuraminidase, protrude from the surface of the influenza virus. Their detection by the immune system allows the host organism to mount defences against the viral threat. The virus evolves in response to this pressure, which manifests as changes in the appearance of its hemagglutinin and neuraminidase. This process, known as antigenic drift, leads to the proteins evading detection. It is also why flu vaccines require frequent updates, as they rely on 'training' the immune system to recognise the most important strains in circulation ­ primarily by exposing it to appropriate versions of hemagglutinin. While the antigenic drift of hemagglutinin has been extensively studied, much less is known about how the neuraminidase accumulates mutations, and how these affect the immune response. To investigate this question, Catani et al. selected 43 genetically distant neuraminidases from human viral samples isolated between 2009 and 2017. Statistical analyses were applied to define their relatedness, revealing that a group of closely related neuraminidases predominated from 2009 to 2015, before they were being taken over by a second group. A third group, which was identified in viruses isolated in 2013, was remarkably close to the neuraminidase of strains that circulated in the late 1990s. The fourth and final group of neuraminidases was derived from influenza viruses that normally circulate in pigs but can also occasionally infect humans. Next, Catani et al. examined the immune response that these 43 neuraminidases could elicit in mice, as well as in ferrets ­ the animal most traditionally used in influenza research. This allowed them to pinpoint which changes in the neuraminidase sequences were important to escape recognition by the host. Data obtained from the two model species were comparable, suggesting that these experiments could be conducted on mice going forward, which are easier to work with than ferrets. Finally, Catani et al. used machine learning to build a computational model that could predict how strongly the immune system would respond to a specific neuraminidase variant. These findings could help guide the development of new vaccines that include neuraminidases tailored to best prime and train the immune system against a larger variety of strains. This may aid the development of 'supra-seasonal' vaccines that protect against a broad range of influenza viruses, reducing the need for yearly updates.

Effects and mechanism of Qingke Pingchuan granules against influenza virus infection.

Qingke Pingchuan granules (QPGs), which contain Houttuynia cordata Thunb, Fritillaria cirrhosa, fired licorice, and fired bitter almonds, among other components, can clear heat and ventilate the lungs, relieving cough and asthma. Clinically, QPGs are mainly used to treat cough, asthma, fever and other discomforts caused by acute or chronic bronchitis. In this study, the antiviral activity of QPGs against respiratory syncytial virus (RSV), influenza A virus A/FM/1/47 (H1N1), oseltamivir-resistant H1N1, A/Beijing/32/92 (H3N2), Sendai virus, and human adenovirus type 3 in Hep-2 or MDCK cells was evaluated using the CCK-8 method, and the cytotoxicity of QPGs to these two cell lines was tested. The effect of QPGs on mice infected with influenza A virus A/FM/1/47 (H1N1) was evaluated by measuring body weight, survival time, and survival rate, as well as virus titers and lesions in the lungs and levels of inflammatory factors in serum. In addition, the expression of TLR-7-My88-NF-κB signaling pathway-related proteins in lung tissues was analyzed by Western blotting and qRT-PCR. The results showed that QPGs had a potent inhibitory effect on the six viruses tested in vitro. Interestingly, QPGs also displayed particularly pronounced antiviral activity against H1N1-OC, similar to that of oseltamivir, a well-known antiviral drug. QPGs effectively protected mice from infection by H1N1, as indicated by significantly increased body weights, survival times, and survival rates and reduced lung virus titers of inflammatory factors and lung tissue injury. The levels of TLR-7-MyD88-NF-κB-pathway-related proteins in the lung tissue of infected mice were found to be decreased after QPG treatment, thereby alleviating lung injury caused by excessive release of inflammatory factors. Taken together, these findings indicate that QPGs have satisfactory activity against influenza virus infection.

MUC5AC: A potential biomarker of severity in pediatric patients infected with influenza.

Numerous factors can increase the risk of severe influenza; however, a majority of severe cases occur in previously healthy children. Identification of high-risk children is important for targeted preventive interventions and prompt treatment. The aim of this study was to evaluate MUC5AC as a biomarker for influenza disease severity in children. For this, a prospective cohort study was conducted in 2019. Children hospitalized with acute respiratory infection (ARI) with confirmed positive influenza infection were enrolled. Influenza cases were identified by reverse transcriptase-polymerase chain reaction. Life-threatening disease (LTD) was defined by the need for intensive care and ventilatory support. MUC5AC, epidemiologic, and clinical risk factors were assessed. Three hundred and forty-two patients were hospitalized with ARI, of which 49 (14%) had confirmed influenza infection and 6 (12%) of them developed LTD. MUC5AC levels were higher in those patients with mild disease compared to cases with poorer outcomes. Our results show that the severity of influenza infection in children is significantly associated with low levels of MUC5AC. These findings suggest its potential as a suitable biomarker for predicting disease severity.

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.

[RESUMEN SEMANAL]. Situación regional: Durante las últimas cuatro semanas epidemiológicas (SE) se han observado niveles bajos en la actividad de la Enfermedad Tipo Influenza (ETI) en la región de las Américas, con una tendencia decreciente. Ésta se ha relacionado principalmente con la actividad observada en Norteamérica. A su vez se ha observado una disminución en la actividad de Infección Respiratoria Aguda Grave (IRAG), actualmente en niveles bajos. En ambos casos la actividad observada se ha asociado a casos positivos de influenza y en menor medida de SARS-CoV-2. En cuanto a la circulación de virus respiratorios, a nivel regional la actividad de SARS-CoV-2 ha descendido a niveles bajos en comparación con olas epidémicas previas. Asimismo, se ha observado una actividad epidémica de influenza para esta época del año que se mantiene en ligero descenso, y una actividad en descenso del Virus Respiratorio Sincitial (VRS) que se encuentra actualmente en niveles bajos. América del Norte: Los casos de ETI, se han mantenido en descenso durante las cuatro últimas SE, presentando niveles intermedio-bajos y siendo la mayoría de los casos atribuibles a influenza. Las hospitalizaciones asociadas a virus respiratorios se han mantenido en descenso y en niveles bajos. La actividad de influenza se ha mantenido en niveles epidémicos de circulación, mostrando un descenso durante las cuatro últimas SE. Durante este periodo, los virus de influenza predominantes han sido del tipo B/Victoria, con circulación en menor medida de influenza A(H3N2) y A(H1N1)pdm09. La actividad del VRS ha mostrado un descenso en las últimas cuatro SE, manteniéndose en niveles bajos. La actividad del SARS-CoV-2 se ha mantenido en niveles bajos. Por países: En Canadá, la actividad del SARS-CoV-2 se ha mantenido en niveles bajos. La actividad de influenza se ha mantenido en niveles epidémicos con un descenso paulatino, y la actividad del VRS ha permanecido en descenso encontrándose en niveles bajos. En México, la circulación de influenza se ha mantenido fluctuante en niveles epidémicos en las cuatro últimas SE, y la circulación del SARS-CoV-2 ha presentado un descenso hasta niveles bajos. En Estados Unidos, la actividad de influenza ha mostrado un descenso en las cuatro últimas SE, aunque se mantiene por encima del umbral epidémico. Tanto el VRS como el SARS-CoV-2 han mantenido una actividad en descenso hasta niveles bajos. Los casos de ETI han mostrado un descenso y se mantienen en niveles medio-bajos. Las tasas de hospitalización por influenza, VRS y SARSCoV- 2 han presentado una tendencia decreciente en las cuatro últimas SE, con niveles bajos. Caribe: Los casos de ETI y de IRAG han permanecido en descenso durante las cuatro últimas semanas, siendo la mayoría de los casos positivos atribuibles a influenza y en menor medida SARS-CoV-2. La actividad de influenza se ha mantenido fluctuante en niveles bajos durante las últimas cuatro SE. Durante este periodo, los virus predominantes han sido de tipo A(H3N2), con circulación concurrente de influenza A(H1N1)pdm09 y en menor medida B/Victoria. La actividad del VRS se ha mantenido en niveles bajos. La actividad del SARS-CoV-2 ha permanecido en niveles bajos. Por países: Se ha observado actividad de influenza las últimas cuatro SE en Belice, Jamaica, Guyana y las Islas Caimán. Se ha observado actividad de SARS-CoV-2 en Barbados, Guyana y Trinidad y Tobago. América Central: Durante las cuatro últimas SE la actividad tanto de ETI como de IRAG se ha mantenido baja, aunque presentando un ligero incremento, con la mayoría de los casos positivos atribuibles a influenza. La actividad de influenza ha presentado un ligero incremento durante este periodo situándose en niveles intermedio-bajos. En las cuatro últimas SE, los virus influenza predominantes han sido de tipo A(H3N2) con circulación concurrente de A(H1N1)pdm09. La actividad del VRS y del SARS-CoV-2 ha permanecido en niveles bajos. Por países: En El Salvador, la actividad de IRAG se encuentra en torno a niveles epidémicos con una circulación de SARS-CoV-2 en niveles bajos y una actividad de influenza fluctuando en torno al umbral epidémico. En Guatemala durante las cuatro últimas SE, se ha observado una actividad de ETI e IRAG estable en niveles epidémicos, asociada a casos positivos de influenza, cuya circulación se encuentra en niveles moderados. En Honduras, en las cuatro últimas SE, se ha observado una actividad fluctuante de IRAG en torno a niveles epidémicos, asociada a casos positivos de influenza, cuya actividad se encuentra en niveles epidémicos y en descenso. En Nicaragua, la actividad tanto del VRS, influenza y SARS-CoV-2 se encuentra en niveles bajos. En Panamá los casos de ETI e IRAG han mostrado un incremento en las cuatro últimas SE, y la actividad de influenza se encuentra en niveles epidémicos. Andina: La actividad de ETI se ha mantenido estable en niveles bajos durante las cuatro últimas SE. Los casos de IRAG se han mantenido estables con niveles bajos, sin embrago se ha observado un ascenso en la proporción de casos positivos a VRS y en menor medida influenza. La actividad de influenza ha permanecido en niveles bajos en las cuatro últimas SE con una tendencia fluctuante. Durante este periodo, los virus de influenza predominantes han sido de tipo A(H3N2) con circulación concurrente de A(H1N1)pdm09. La actividad del VRS se ha mantenido en niveles bajos, aunque con una tendencia creciente. La actividad de SARS-CoV-2 se ha mantenido en descenso con niveles bajos. Por países: En Colombia, el VRS aunque en niveles bajos ha presentado un incremento e las cuatro últimas SE, la actividad de SARS-CoV-2 ha presentado un descenso situándose en niveles bajos y la actividad de influenza se ha mantenido por debajo del umbral epidémico con un ligero incremento. La actividad de IRAG se ha mantenido en torno al umbral epidémico durante este periodo, con los casos positivos atribuibles a VRS e influenza. En Ecuador, tras el marcado incremento en la actividad de VRS observado en SE previas, se ha detectado un descenso hasta niveles medios, el SARS-CoV-2 ha presentado un descenso situándose en niveles bajos y la actividad de influenza se ha ascendido superando el umbral epidémico. La actividad de IRAG se encuentra en niveles epidémicos y los casos positivos han sido atribuibles en su mayoría a VRS y en menor medida influenza. En Perú la actividad de influenza se encuentra oscilante en torno al umbral epidémico y la actividad de SARS-CoV-2 ha descendido a nieves bajos. En Venezuela, durante las últimas cuatro SE, se ha observado un una actividad fluctuante de influenza en torno al umbral epidémico. Brasil y el Cono Sur: La actividad de ETI e IRAG ha presentado un incremento en las cuatro últimas SE situándose en niveles intermedios, con la mayoría de los casos positivos atribuibles a influenza. La actividad de influenza ha presentado un incremento en las últimas cuatro SE con niveles epidémicos en la mayoría de los países. En este periodo, los virus de influenza predominantes han sido de tipo A(H3N2) y en menor medida A(H1N1)pdm09. La actividad del VRS se ha mantenido en niveles bajos, aunque con un ligero incremento. La actividad del SARS-CoV-2 se ha mantenido en descenso con niveles bajos de actividad. Por países: En Argentina, los niveles de ETI e IRAG han permanecido por debajo del umbral epidémico. La actividad de influenza ha presentado un incremento con niveles por encima del umbral epidémico y el porcentaje de positividad de SARSCoV- 2, se ha mantenido en descenso situándose en niveles bajos. A su vez se ha observado un ligero incremento en el porcentaje de positividad de VRS. En Brasil, la actividad del SARS-CoV-2 ha permanecido en descenso, con niveles bajos, y la actividad de influenza se mantiene por debajo del umbral epidémico. En Chile, tanto los casos de ETI como de IRAG han presentado un ascenso en las cuatro últimas SE situándose en niveles extraordinarios y epidémicos respectivamente; la mayoría de los casos positivos son atribuibles a influenza que circula con niveles extraordinarios. En Paraguay, la actividad de IRAG ha superado el umbral epidémico y la actividad de ETI se ha mantenido por debajo este umbral. La actividad de influenza se encuentra en torno al umbral epidémico; la circulación del SARS-CoV-2 y del VRS se encuentra estable en niveles bajos. En Uruguay, la actividad de IRAG ha superado el umbral epidémico, con la mayoría de los casos positivos atribuibles a SARS-CoV-2 e influenza, cuya actividad ha superado umbral epidémico.

Regional Update, Influenza and Other Respiratory Viruses. Epidemiological Week 19 (17 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. 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, SARSCoV- 2. Regionally, SARS-CoV-2 activity has decreased to low levels compared to previous epidemic waves. Additionally, influenza epidemic activity has been observed for this time of year, while Respiratory Syncytial Virus (RSV) activity is declining and currently at low levels. North America: ILI cases have continued to decline over the past four EWs, reaching intermediate-low levels, with most cases attributed to influenza. Hospitalizations associated with respiratory viruses have also declined and remain low. Influenza activity has stayed at epidemic levels, showing a decrease over the last four EWs. During this period, the predominant influenza viruses have been B/Victoria, with lesser circulation of influenza A(H3N2) and A(H1N1)pdm09. RSV activity has decreased over the past four EWs, remaining at low levels. SARS-CoV-2 activity has remained low, though with a slight increase. By country: In Canada, SARS-CoV-2 activity has stayed low. Influenza activity has remained at epidemic levels but is gradually declining, and RSV activity has continued to decrease, remaining low. In Mexico, influenza circulation has fluctuated at epidemic levels over the past four EWs, and SARS-CoV-2 circulation has decreased to low levels. In the United States, influenza activity has decreased to low levels over the past four EWs. Both RSV and SARS-CoV-2 have remained at low levels. ILI cases have shown a decline and remain at medium-low levels. Hospitalization rates for influenza, RSV, and SARS-CoV-2 have shown a decreasing trend over the past four EWs, reaching low levels. Caribbean: ILI and SARI cases have continued to decline over the past four weeks, with most positive cases attributed to influenza and, to a lesser extent, SARS-CoV-2. Influenza activity has fluctuated at low levels over the past four EWs. During this period, the predominant viruses have been type A(H3N2), with concurrent circulation of influenza A(H1N1)pdm09 and, to a lesser extent, B/Victoria. RSV activity has remained low. SARS-CoV-2 activity has shown a marked increase over the past two weeks. By country: Influenza activity has been observed over the past four EWs in Belize, Guyana, and the Cayman Islands. SARS-CoV- 2 activity has been noted in Barbados and the Cayman Islands. Central America: Over the past four EWs, both ILI and SARI activity has remained low, though with a slight increase, with most positive cases attributed to influenza. Influenza activity has shown a slight increase during this period, reaching intermediate levels. Over the past four EWs, the predominant influenza viruses have been A(H3N2) with concurrent circulation of A(H1N1)pdm09. RSV and SARS-CoV-2 activity have remained low. By country: In El Salvador, SARI activity is around epidemic levels with low circulation of SARS-CoV-2 and fluctuating influenza activity around the epidemic threshold. In Guatemala, during the past four EWs, ILI and SARI activity has been stable at epidemic levels, associated with positive influenza cases circulating at moderate levels. In Honduras, during the past four EWs, SARI activity has fluctuated around epidemic levels, associated with positive influenza cases circulating at epidemic levels and in decline. In Nicaragua, RSV, influenza, and SARS-CoV-2 activity are at low levels. In Panama, ILI and SARI cases have shown an increase over the past four EWs, with influenza activity at epidemic levels. Andean Region: ILI activity has remained stable at low levels over the past four EWs. SARI cases have remained stable at low levels; however, there has been an increase in the proportion of positive cases for RSV and, to a lesser extent, influenza. Influenza activity has remained at low levels over the past four EWs with a fluctuating trend. During this period, the predominant influenza viruses have been type A(H3N2) with concurrent circulation of type A(H1N1)pdm09. RSV activity has remained at low levels, though with an increasing trend. SARS-CoV-2 activity has continued to decline, remaining at low levels. By country: In Colombia, RSV activity, although low, has increased over the past four EWs; SARS-CoV-2 activity has decreased to low levels, and influenza activity has remained below the epidemic threshold with a slight increase. SARI activity has hovered around the epidemic threshold during this period, with positive cases attributed to RSV and influenza. In Ecuador, following a marked increase in RSV activity in previous EWs, there has been a decline to medium levels; SARS-CoV-2 activity has decreased to low levels, and influenza activity has risen above the epidemic threshold. SARI activity is at epidemic levels, with most positive cases attributed to RSV and, to a lesser extent, influenza. In Peru, influenza activity is fluctuating around the epidemic threshold, and SARS-CoV-2 activity has decreased to low levels. In Venezuela, during the past four EWs, influenza activity has fluctuated around the epidemic threshold. Brazil and the Southern Cone: ILI and SARI activity have increased over the past four EWs to intermediate-high levels, with most positive cases attributed to influenza. Influenza activity has increased over the past four EWs, reaching epidemic levels in most countries. During this period, the predominant influenza viruses have been type A(H3N2) and, to a lesser extent, A(H1N1)pdm09. RSV activity has remained low, though with a slight increase. SARS-CoV-2 activity has continued to decline, remaining at low levels. By country: In Argentina, ILI and SARI levels have remained below the epidemic threshold. Influenza activity has increased to levels above the epidemic threshold, and the positivity rate for SARS-CoV-2 has continued to decline, reaching low levels. There has also been a slight increase in the positivity rate for RSV. In Brazil, SARS-CoV-2 activity has continued to decline, reaching low levels, and influenza activity remains below the epidemic threshold. In Chile, both ILI and SARI cases have increased over the past four EWs, reaching extraordinary and epidemic levels, respectively, with most positive cases attributed to influenza circulating at extraordinary levels. In Paraguay, SARI activity has exceeded the epidemic threshold, and ILI activity has remained below this threshold. Influenza activity is at epidemic levels; SARS-CoV-2 and RSV circulation remain stable at low levels. In Uruguay, SARI activity has exceeded the epidemic threshold, with most positive cases attributed to SARS-CoV-2 and influenza, whose activity has exceeded the epidemic threshold.

[RESUMEN SEMANAL]. Situación regional: Durante las últimas cuatro semanas epidemiológicas (SE) se han observado niveles bajos en la actividad de la Enfermedad Tipo Influenza (ETI) en la región de las Américas, con una tendencia decreciente. A su vez se ha observado una disminución en la actividad de Infección Respiratoria Aguda Grave (IRAG), actualmente en niveles bajos. En ambos casos la actividad observada se ha asociado a casos positivos de influenza y en menor medida de SARS-CoV-2. En cuanto a la circulación de virus respiratorios, a nivel regional la actividad de SARS-CoV-2 ha descendido a niveles bajos en comparación con olas epidémicas previas. Asimismo, se ha observado una actividad epidémica de influenza para esta época del año, y una actividad en descenso del Virus Respiratorio Sincitial (VRS) que se encuentra actualmente en niveles bajos. América del Norte: Los casos de ETI, se han mantenido en descenso durante las cuatro últimas SE, presentando niveles intermedio-bajos y siendo la mayoría de los casos atribuibles a influenza. Las hospitalizaciones asociadas a virus respiratorios se han mantenido en descenso y en niveles bajos. La actividad de influenza se ha mantenido en niveles epidémicos de circulación, mostrando un descenso durante las cuatro últimas SE. Durante este periodo, los virus de influenza predominantes han sido del tipo B/Victoria, con circulación en menor medida de influenza A(H3N2) y A(H1N1)pdm09. La actividad del VRS ha mostrado un descenso en las últimas cuatro SE, manteniéndose en niveles bajos. La actividad del SARS-CoV-2 se ha mantenido en niveles bajos, aunque con un ligero incremento. Por países: En Canadá, la actividad del SARS-CoV-2 se ha mantenido en niveles bajos. La actividad de influenza se ha mantenido en niveles epidémicos con un descenso paulatino, y la actividad del VRS ha permanecido en descenso encontrándose en niveles bajos. En México, la circulación de influenza se ha mantenido fluctuante en niveles epidémicos en las cuatro últimas SE, y la circulación del SARS-CoV-2 ha presentado un descenso hasta niveles bajos. En Estados Unidos, la actividad de influenza ha mostrado un descenso en las cuatro últimas SE hasta niveles bajos. Tanto el VRS como el SARS-CoV- 2 han mantenido niveles bajos. Los casos de ETI han mostrado un descenso y se mantienen en niveles medio-bajos. Las tasas de hospitalización por influenza, VRS y SARS-CoV-2 han presentado una tendencia decreciente en las cuatro últimas SE, con niveles bajos. Caribe: Los casos de ETI y de IRAG han permanecido en descenso durante las cuatro últimas semanas, siendo la mayoría de los casos positivos atribuibles a influenza y en menor medida SARS-CoV-2. La actividad de influenza se ha mantenido fluctuante en niveles bajos durante las últimas cuatro SE. Durante este periodo, los virus predominantes han sido de tipo A(H3N2), con circulación concurrente de influenza A(H1N1)pdm09 y en menor medida B/Victoria. La actividad del VRS se ha mantenido en niveles bajos. La actividad del SARS-CoV-2 ha presentado un marcado incremento en las dos últimas semanas. Por países: Se ha observado actividad de influenza las últimas cuatro SE en Belice, Guyana y las Islas Caimán. Se ha observado actividad de SARS-CoV-2 en Barbados y las Islas Caimán. América Central: Durante las cuatro últimas SE la actividad tanto de ETI como de IRAG se ha mantenido baja, aunque presentando un ligero incremento, con la mayoría de los casos positivos atribuibles a influenza. La actividad de influenza ha presentado un ligero incremento durante este periodo situándose en niveles intermedios. En las cuatro últimas SE, los virus influenza predominantes han sido de tipo A(H3N2) con circulación concurrente de A(H1N1)pdm09. La actividad del VRS y del SARS-CoV-2 ha permanecido en niveles bajos. Por países: En El Salvador, la actividad de IRAG se encuentra en torno a niveles epidémicos con una circulación de SARS-CoV-2 en niveles bajos y una actividad de influenza fluctuando en torno al umbral epidémico. En Guatemala durante las cuatro últimas SE, se ha observado una actividad de ETI e IRAG estable en niveles epidémicos, asociada a casos positivos de influenza, cuya circulación se encuentra en niveles moderados. En Honduras, en las cuatro últimas SE, se ha observado una actividad fluctuante de IRAG en torno a niveles epidémicos, asociada a casos positivos de influenza, cuya actividad se encuentra en niveles epidémicos y en descenso. En Nicaragua, la actividad tanto del VRS, influenza y SARS-CoV-2 se encuentra en niveles bajos. En Panamá los casos de ETI e IRAG han mostrado un incremento en las cuatro últimas SE, y la actividad de influenza se encuentra en niveles epidémicos. Andina: La actividad de ETI se ha mantenido estable en niveles bajos durante las cuatro últimas SE. Los casos de IRAG se han mantenido estables con niveles bajos, sin embrago se ha observado un ascenso en la proporción de casos positivos a VRS y en menor medida influenza. La actividad de influenza ha permanecido en niveles bajos en las cuatro últimas SE con una tendencia fluctuante. Durante este periodo, los virus de influenza predominantes han sido de tipo A(H3N2) con circulación concurrente de A(H1N1)pdm09. La actividad del VRS se ha mantenido en niveles bajos, aunque con una tendencia creciente. La actividad de SARS-CoV-2 se ha mantenido en descenso con niveles bajos. Por países: En Colombia, el VRS aunque en niveles bajos ha presentado un incremento en las cuatro últimas SE, la actividad de SARS-CoV-2 ha presentado un descenso situándose en niveles bajos y la actividad de influenza se ha mantenido por debajo del umbral epidémico con un ligero incremento. La actividad de IRAG se ha mantenido en torno al umbral epidémico durante este periodo, con los casos positivos atribuibles a VRS e influenza. En Ecuador, tras el marcado incremento en la actividad de VRS observado en SE previas, se ha detectado un descenso hasta niveles medios, el SARS-CoV-2 ha presentado un descenso situándose en niveles bajos y la actividad de influenza se ha ascendido superando el umbral epidémico. La actividad de IRAG se encuentra en niveles epidémicos y los casos positivos han sido atribuibles en su mayoría a VRS y en menor medida influenza. En Perú la actividad de influenza se encuentra oscilante en torno al umbral epidémico y la actividad de SARS-CoV-2 ha descendido a nieves bajos. En Venezuela, durante las últimas cuatro SE, se ha observado un una actividad fluctuante de influenza en torno al umbral epidémico. Brasil y el Cono Sur: La actividad de ETI e IRAG ha presentado un incremento en las cuatro últimas SE situándose en niveles intermedio-altos, con la mayoría de los casos positivos atribuibles a influenza. La actividad de influenza ha presentado un incremento en las últimas cuatro SE con niveles epidémicos en la mayoría de los países. En este periodo, los virus de influenza predominantes han sido de tipo A(H3N2) y en menor medida A(H1N1)pdm09. La actividad del VRS se ha mantenido en niveles bajos, aunque con un ligero incremento. La actividad del SARS-CoV-2 se ha mantenido en descenso con niveles bajos de actividad. Por países: En Argentina, los niveles de ETI e IRAG han permanecido por debajo del umbral epidémico. La actividad de influenza ha presentado un incremento con niveles por encima del umbral epidémico y el porcentaje de positividad de SARSCoV- 2, se ha mantenido en descenso situándose en niveles bajos. A su vez se ha observado un ligero incremento en el porcentaje de positividad de VRS. En Brasil, la actividad del SARS-CoV-2 ha permanecido en descenso, con niveles bajos, y la actividad de influenza se mantiene por debajo del umbral epidémico. En Chile, tanto los casos de ETI como de IRAG han presentado un ascenso en las cuatro últimas SE situándose en niveles extraordinarios y epidémicos respectivamente; la mayoría de los casos positivos son atribuibles a influenza que circula con niveles extraordinarios. En Paraguay, la actividad de IRAG ha superado el umbral epidémico y la actividad de ETI se ha mantenido por debajo este umbral. La actividad de influenza se encuentra en niveles epidémicos; la circulación del SARS-CoV-2 y del VRS se encuentra estable en niveles bajos. En Uruguay, la actividad de IRAG ha superado el umbral epidémico, con la mayoría de los casos positivos atribuibles a SARSCoV- 2 e influenza, cuya actividad ha superado umbral epidémico.

Pandemic preparedness through vaccine development for avian influenza viruses.

Influenza A viruses pose a significant threat to global health, impacting both humans and animals. Zoonotic transmission, particularly from swine and avian species, is the primary source of human influenza outbreaks. Notably, avian influenza viruses of the H5N1, H7N9, and H9N2 subtypes are of pandemic concern through their global spread and sporadic human infections. Preventing and controlling these viruses is critical due to their high threat level. Vaccination remains the most effective strategy for influenza prevention and control in humans, despite varying vaccine efficacy across strains. This review focuses specifically on pandemic preparedness for avian influenza viruses. We delve into vaccines tested in animal models and summarize clinical trials conducted on H5N1, H7N9, and H9N2 vaccines in humans.

Electronic Health Record-Based Algorithm for Monitoring Respiratory Virus-Like Illness.

Viral respiratory illness surveillance has traditionally focused on single pathogens (e.g., influenza) and required fever to identify influenza-like illness (ILI). We developed an automated system applying both laboratory test and syndrome criteria to electronic health records from 3 practice groups in Massachusetts, USA, to monitor trends in respiratory viral-like illness (RAVIOLI) across multiple pathogens. We identified RAVIOLI syndrome using diagnosis codes associated with respiratory viral testing or positive respiratory viral assays or fever. After retrospectively applying RAVIOLI criteria to electronic health records, we observed annual winter peaks during 2015-2019, predominantly caused by influenza, followed by cyclic peaks corresponding to SARS-CoV-2 surges during 2020-2024, spikes in RSV in mid-2021 and late 2022, and recrudescent influenza in late 2022 and 2023. RAVIOLI rates were higher and fluctuations more pronounced compared with traditional ILI surveillance. RAVIOLI broadens the scope, granularity, sensitivity, and specificity of respiratory viral illness surveillance compared with traditional ILI surveillance.