搜索结果：Influenza and other respiratory viruses

In 2019, pneumonia caused 740,180 deaths in children under five years of age, representing 22% of global mortality in this age group. During the COVID-19 pandemic, public health interventions markedly reduced the circulation of most respiratory viruses other than SARS-CoV-2, leading to significant post-pandemic shifts in respiratory pathogen epidemiology. This study aimed to characterize the epidemiology, clinical features, and risk factors associated with respiratory viruses and bacteria causing pneumonia in Mexican children during the late pandemic and post pandemic periods. Children younger than 14 years with pneumonia were recruited from seven hospitals in Mexico. Demographic and clinical data were collected, and nasopharyngeal swabs were analyzed using a multiplex PCR panel detecting 19 viruses and 7 bacteria. Univariate, bivariate, and logistic regression analyses were performed (SPSS v25). A total of 1715 children were included: 704 during the pandemic (2021-2023) and 1011 post-pandemic (2023-2025). Co-infections (72% vs. 65%, p < 0.001), virus-virus co-infections (25% vs. 11%, p < 0.001), and single viral infections (20% vs. 15%, p = 0.007) were more frequent during the pandemic. Pathogen detection was high in both periods, though negative samples increased post-pandemic (5.4% vs. 15%, p < 0.001). During the pandemic, the 5 most frequently detected pathogens were rhinovirus (66%), RSV A and B (38%), Streptococcus pneumoniae (30%), Haemophilus influenzae (28%), human metapneumovirus (13%). In the post-pandemic period, the 5 most frequently detected pathogens were rhinovirus (52%), Haemophilus influenzae (36%), Streptococcus pneumoniae (35%), RSV A and B (28%), metapneumovirus (11%). Rhinovirus and RSV predominated during the pandemic, whereas Haemophilus influenzae, Streptococcus pneumoniae, parainfluenza viruses, Bordetella pertussis, and Mycoplasma pneumoniae significantly increased post-pandemic. Pediatric pneumonia epidemiology shifted from a predominantly viral profile during the pandemic to increased bacterial detections and virus-bacteria co-infections post-pandemic, alongside re-emergence of typical RSV and influenza seasonality. Higher mean age and rhinovirus as the most frequent pathogen persist after the pandemic. Sustained molecular surveillance and reinforced vaccination programs remain essential in the post-pandemic era.

Quantifying the burden of respiratory syncytial virus (RSV) in adults is challenging compared to influenza, and data among older adults remain scarce in Japan. Country-specific evidence is essential to support RSV vaccination policy. This prospective, multicenter study (APSG-J2) targeted hospitalized adults with community-acquired pneumonia (CAP) and other acute respiratory infections (ARI) in seven community hospitals across four catchment areas in Japan between September 2022 and August 2024. Respiratory samples were analyzed using a multiplex polymerase chain reaction (PCR) kit to detect RSV and influenza. Incidence rates of RSV- and influenza-associated hospitalizations were estimated using study data and national statistics, stratified by age and region. Among 3047 hospitalized patients with CAP/ARI, 1499 (49.2%) underwent multiplex PCR testing. RSV and influenza were detected in 2.8% and 3.3% of tested patients, respectively. The incidences of RSV-associated CAP/ARI hospitalizations among adults aged &#x2265;&#x2009;65&#x2009;years were 29 and 36 per 100,000 person-years in the first and second years, respectively, with higher incidences among those aged &#x2265;&#x2009;85&#x2009;years (150 and 131 per 100,000 person-years). Influenza incidence increased markedly in the second year (from 11 to 71 per 100,000 person-years for adults age &#x2265;&#x2009;65&#x2009;years), possibly reflecting post-COVID-19 transmission changes. In this multicenter study, we estimated the incidence of RSV- and influenza-associated hospitalizations among adults in Japan. The findings indicated that the incidence increased with age, and influenza-associated hospitalizations increased in the second year. Continued surveillance is essential to accurately assess RSV burden in the adult population.

The emergence of SARS-CoV-2 and introduction of COVID-19 vaccines into immunologically na&#xef;ve populations may alter the dynamics of other acute viral respiratory infections (viral ARIs) and vice versa. Competing forces, including viral interference, cross-reactive immunity, shared susceptibility, and immune dysregulation, may affect the risk. The potential net impact of various immune-priming events and their timing on the risk of viral ARIs is largely unknown. Using data from the National Clinical Cohort Collaborative (N3C) COVID-19 Enclave, this retrospective population-based cohort study investigated the relationship between immune-priming events (COVID-19 and influenza vaccinations, and SARS-CoV-2, influenza, other, and unspecified viral ARIs) between January 2018 and September 2021 and the risk of viral ARIs during October 2021-April 2022. The sample included N&#x2009;=&#x2009;608,725 individuals from seven data partners with well-ascertained COVID-19 and influenza vaccination data. Early COVID-19 vaccination (December 2020-March 2021) and SARS-CoV-2 infection during the overlapping period (October 2020-March 2021) were associated with a lower risk of all outcomes, including non-SARS-CoV-2 infections. Off-season influenza vaccination (January-June 2021) was associated with a lower risk of SARS-CoV-2 and any viral ARI. Other priming events showed mixed associations, with a lack of evidence of stronger protection from more recent immune-priming events. This exploratory analysis suggests potential crossprotection between viral ARIs that may inform vaccination strategies. While ascertainment and healthcare-seeking biases in electronic health records may inflate positive associations between infection outcomes and immune priming, negative (i.e., protective) associations are of potential public health significance and warrant further investigation.

Respiratory viruses, frequently detected in asthma, are associated with worse outcomes. This meta-analysis systematically quantifies the prevalence of respiratory viruses in stable and acute asthma, across children and adults, and explores factors associated with increased viral burden through meta-regression. This prospectively registered meta-analysis (PROSPERO-CRD42023375108) included studies employing molecular techniques to assess respiratory virus prevalence in asthma. Three databases were searched in August 2024. Risk of bias and certainty of evidence were assessed. We performed random-effects meta-analysis of proportions. We included 111 eligible studies. Moderate-certainty evidence indicated a pooled prevalence of any respiratory virus of 33.9% (95% confidence interval 24.8-43.7%) in children and 23.0% (12.9-35.0%) in adults with stable asthma. In acute asthma, prevalence increased to 58.8% (52.5-65.0%) in children and 49.9% (41.2-58.5%) in adults (moderate certainty). Rhinovirus was the most frequently identified virus, especially in acute asthma (45.0% in children versus 21.2% in adults). Respiratory syncytial virus and bocavirus were more common in younger children, while coronavirus and influenza were more frequently detected in adults; respiratory syncytial virus peaked in older adults too. A higher prevalence of influenza virus B and adenovirus in children, and of influenza virus A and parainfluenza 2 in adults with severe versus non-severe acute asthma suggests a potential association with more severe acute attacks. Respiratory viruses are common in both stable and acute asthma. This suggests that the diagnostic value of a positive viral test during acute episodes may be limited and could benefit from complementary biomarkers to improve interpretation.

This first-in-human, randomized, controlled, phase 1 proof-of-principle study evaluated the safety, reactogenicity, and immunogenicity of an investigational mRNA-based monovalent influenza vaccine encoding influenza A/H1N1&#xa0;hemagglutinin (FLUmHA). Younger adults (YA) aged 18-45&#x2009;y received one dose of FLUmHA at one of 10 dose levels (0.5-100&#x2009;&#xb5;g, n&#x2009;=&#x2009;24/25 per group) or licensed Flu Dresden-quadrivalent seasonal influenza vaccine (Flu D-QIV, n&#x2009;=&#x2009;35) on day (D)1. Older adults (OA) aged 60-80&#x2009;y received FLUmHA (18&#x2009;&#xb5;g, n&#x2009;=&#x2009;32) or Flu D-QIV (n&#x2009;=&#x2009;16). Reporting rates for solicited adverse events (AEs) occurring within 7&#x2009;d post-vaccination generally increased with increasing FLUmHA dose levels, and were 62.5%-100% (severe: 0.0%-20.8%) in YA across FLUmHA dose levels versus 88.6% (severe: 2.9%) in Flu D-QIV-vaccinated YA, and 62.5% (severe: 0.0%) (FLUmHA) versus 56.3% (severe: 0.0%) (Flu D-QIV) in OA. Unsolicited AEs within 28&#x2009;d post-vaccination were reported by 50.0%-70.8% of YA across FLUmHA dose levels versus 68.6% of Flu D-QIV-vaccinated YA, and by 43.8% (FLUmHA) versus 50.0% (Flu D-QIV) of OA. No safety concerns were identified. A/H1N1&#xa0;hemagglutination inhibition titers increased from pre-vaccination to D22, with adjusted geometric mean increases (GMIs) of 6.2-36.7 across YA and OA groups; the observed response was dose-dependent and higher in FLUmHA (for doses&#x2009;> 1&#x2009;&#xb5;g) versus Flu D-QIV recipients. Titers decreased but remained above pre-vaccination levels at D183 (GMI: 2.9-14.0). Additionally, FLUmHA elicited a numerically higher hemagglutinin-specific CD4+ T-cell response (predominantly Th1 profile) than Flu D-QIV, both in YA and OA. These results support the progression to clinical development of a multivalent mRNA Flu vaccine candidate.Trial registration: NCT05446740. What is the context? Seasonal flu is a common respiratory illness caused by influenza viruses. Most people only have mild symptoms, but flu can also be serious and lead to hospitalization and death.Flu vaccines are updated each year to match the most common influenza virus strains expected to be present that year. Because influenza viruses change easily, some years the vaccines do not work as well when strains chosen for the vaccine are a poor match with the circulating strains. Moreover, flu vaccines do not always work well in older adults.Investigational flu vaccines that use messenger RNA (mRNA) technology have been shown to cause a robust and durable immune response, also in older adults. In addition, the production of mRNA vaccines is flexible and scalable, and the vaccines contain the virus&#x2019;s exact genetic code, avoiding the changes that can occur in traditional vaccines grown in eggs. This may lead to a better match between the vaccine and the influenza viruses circulating during the season.What is new? We did a study to collect data on the safety and immune response of an investigational mRNA Flu vaccine targeting one flu strain.The study included 276 adults aged 18&#x2013;45&#x2009;y and 48 adults aged 60&#x2013;80&#x2009;y. Participants received either the mRNA Flu vaccine or a licensed flu vaccine as control. The younger participants receiving mRNA Flu were divided in 10 groups, each getting a different dose of the vaccine. The older participants received one specific dose.We found that side effects after mRNA Flu vaccination were mostly mild or moderate and were short-lived, even at the highest vaccine doses. Only a few serious adverse events occurred, and these were not related to the vaccine.The mRNA Flu vaccine induced an immune response against the flu strain targeted by the vaccine. The immune response was higher than with the control vaccine for most doses and increased with higher doses.What is the impact? The safety data and robust and durable immune response of the tested vaccine support further clinical development of an mRNA Flu vaccine targeting multiple flu strains.

Monitoring antigenic drift in human influenza A viruses is essential for vaccine strain selection and ensuring protection against circulating strains. Antigenic drift is traditionally assessed using ferret antisera, which provide monospecific responses and human vaccinee sera, which reflect exposure to multiple antigens. In this study, we evaluated the pig as an alternative source of antisera to study antigenic drift compared with immune responses in ferrets and humans. We included seasonal influenza A(H1N1pdm09) human viruses that had shown different antigenic characteristics when using ferret or human antisera. Pairs of pigs were inoculated with six human A(H1N1)pdm09 viruses circulating between 2019 and 2023, a period of marked antigenic drift. Pig and ferret antisera raised against these six reference viruses were analysed by haemagglutination inhibition (HI) and virus neutralisation (VN), and homologous and heterologous titre differences were used to assess antigenic reactivity profiles among the viruses between species. Pigs were successfully infected with all strains, shedding virus and producing antibody responses, confirming their susceptibility to human influenza A viruses. Antigenic reactivity of pig antisera was qualitatively comparable to ferret antisera in both HI and VN assays, although maximum homologous antibody titres were significantly higher in ferrets (on average 16-fold for HI and from around 12- to 210-fold for VN). The antisera raised against viruses in circulation in 2019 and before, exemplified by A/Guangdong-Maonan/SWL1536/2019, clade 5a.1, were clearly differentiated by both ferret and pig antisera from those in clade 5a.2 and its derivatives that became predominant. Ferrets and pigs showed comparable responses and both distinguished clade 5a.1 from clade 5a.2. However, neither model recognised antigenically drifted variants from 2019 to 2022, including subclades 5a.2-C, 5a.2a-C.1/C.1.9 and 5a.2a.1-C.1.1/D, which were distinguishable using human postvaccination antisera.

In recent years, wastewater (WW)-based epidemiology has been increasingly used for surveillance of SARS-CoV-2 and has emerged as a potential tool for monitoring other respiratory viruses. Most evidence on the use of WW for detecting multiple respiratory viruses comes from developed countries. In this study, we assessed the feasibility of multi-respiratory virus sewage surveillance in a middle-income country and explored signals that may be potentially used as early warning signs for Public Health authorities. We examined the presence of SARS-CoV-2, influenza virus, respiratory syncytial virus (RSV), and human metapneumovirus (hMPV) in 238 WW samples collected from three treatment plants in San Luis Potos&#xed;, Mexico, over one year. The weekly detection of each virus was compared with the weekly number of hospital admissions for respiratory infections caused by that virus in pediatric patients. SARS-CoV-2, influenza, hMPV, and RSV were detected in 152 (63.9%), 108 (45.4%), 95 (39.9%), and 24 (10.1%) samples, respectively. There was no significant correlation between viral detection in WW and the number of hospitalizations during that week. However, analyses of WW viral detection with hospitalizations in subsequent weeks showed an increasing correlation reaching a maximum correlation for a lag of 12 weeks for SARS-CoV-2 (rs = 0.63, p = 0.001), 9 weeks for influenza (rs 0.62, p = 0.0001), 2 weeks for RSV (rs = 0.30, p = 0.05), and 3 weeks for hMPV (rs = 0.39, p = 0.009). In addition, we identified time-periods of SARS-CoV-2, influenza, and RSV widespread circulation (several consecutive weeks in which viruses were detected in the three treatment plants); most hospitalizations caused by these viruses occurred after widespread circulation was detected in WW, suggesting this may be used as an early alert for public health systems. Overall, our results show that WW-based surveillance of multiple respiratory viruses is feasible and has potential applications as an early warning system in middle-income countries.

Understanding the circulation of influenza A viruses and other respiratory pathogens in Antarctic wildlife is essential for anticipating outbreaks and evaluating potential impacts on vulnerable populations. During the austral summer of December 2024 and January 2025, we conducted viral surveillance in six bird species breeding at Lions Rump, King George Island, South Shetland Islands, Antarctica. A total of 199 individuals were sampled, including Pygoscelis papua (gentoo penguin; n = 81), Pygoscelis adeliae (Ad&#xe9;lie penguin; n = 79), Pygoscelis antarcticus (chinstrap penguin; n = 34), Stercorarius antarcticus (brown skua; n = 2), Chionis albus (snowy sheathbill; n = 2), and Eudyptes chrysolophus (macaroni penguin; n = 1). All cloacal and oropharyngeal swabs tested negative for influenza A viruses and coronaviruses by RT-PCR. Blood samples from 177 birds were screened by enzyme-linked immunosorbent assay, which detected influenza A virus antibodies in 20 individuals (11.3%). Hemagglutination inhibition assays identified subtypes H6 and H11 in two penguins and H1, H5, H6, and H9 in one skua. These findings reveal no evidence of active viral infection during the sampling period but provide serological evidence of past exposure in seabird populations at Lions Rump. Continued surveillance is essential to characterize viral dynamics in Antarctic ecosystems and to support early detection and preparedness for potential incursions of emerging high-pathogenicity influenza A viruses.

Following WHO recommendations issued in 2019 and 2022, the National Influenza Center (NIC) of C&#xf4;te d'Ivoire initiated the integration of Respiratory Syncytial Virus (RSV) and SARS-CoV-2 surveillance into its existing sentinel influenza surveillance to strengthen the monitoring of respiratory viruses. The national influenza sentinel surveillance protocol was revised to include specific requirement of RSV and SARS-CoV-2. Nasopharyngeal swabs were collected between January 2022 and December 2023 for all three viruses and were tested by real time RT-PCR. Only PCR-positive samples with Ct value <&#x2009;28 and adequate sample volume were selected for sequencing. CDC Flu SC2 multiplex rRT-PCR assay and Oxford Nanopore MinION Mk1C were used; influenza sequencing was performed at CDC Atlanta. Phylogenetic analyses were conducted to identify genotypes, lineages, and assess genetic relatedness to global strains. Between January 2022 and December 2023, 8316 samples were tested; 12.6% (n&#x2009;=&#x2009;1044) were positive for at least one of the three viruses. RSV (5.63%) detection in severe acute respiratory infection (SARI) cases increased significantly from 3.4% in 2022 to 8.4% in 2023 (p&#x2009;<&#x2009;0.0001). Similarly, influenza (3.71%) detection in SARI cases rose from 1.3% to 2.6% (p&#x2009;=&#x2009;0.0057). SARS-CoV-2 (3.22%) detection was significantly associated with age (p&#x2009;=&#x2009;0.002). All three viruses circulated year-round with distinct seasonal peaks. Genomic analysis showed that A(H3N2) viruses belonged to clade 3C.2a1b.2a.2, A(H1N1) pdm09 to clade 6B.1A.5a.2 and B/Victoria to clade V1A.3a.2, all aligning with global trends. Among SARS-CoV-2 cases, BA.2 and BA.5 sublineages of Omicron predominated in 2022 while XBB and XBB.1.5 sublineages emerged in 2023. Whole genome sequencing revealed RSV A strains as genotype A.D.5.1 and RSV B as genotype B.D.E.1. Integration of RSV and SARS-CoV-2 into influenza sentinel surveillance has enabled continuous detection and genomic characterization, reinforcing the critical role of integrated sentinel surveillance for timely response to respiratory virus threats.

Influenza B virus (IBV) is a significant pathogen and contributes to seasonal influenza epidemics worldwide yearly. Humans are thought to be a reservoir and amplification host for IBV. However, natural infections of IBVs in other species such as pigs probably from a spillover event from humans can sporadically occur. Here, we examined and compared the replication fitness of two human IBV lineages in swine primary respiratory epithelial cells (nasal turbinate, trachea, and lung). IBV strains used in this study included two Victoria lineage viruses (B/Brisbane/60/2008 (BR08) and B/HongKong/286/2017 (HK17)) and two Yamagata lineage viruses (B/Florida/04/06 (FL06) and B/Utah/09/2014 (UT14)). Results of our experiments showed that IBVs replicated efficiently in swine primary respiratory epithelial cells regardless of the virus lineage with higher titers observed at 33&#xb0;C than at 37&#xb0;C. HK17 (Victoria lineage) grew to the highest titers in nasal turbinate and lung cells, while the other Victoria lineage strain BR08 showed a modest replication fitness. In sum, the swine primary respiratory epithelial cells representing the upper, middle, and lower respiratory tract of swine support IBV replication, which can be further explored as the in vitro model system to study IBV adaptation to swine, the mixing vessel in generating zoonotic influenza viruses.

To describe the positivity, clinical presentation and predictors of respiratory syncytial virus (RSV) in adult primary care patients compared to influenza and SARS-CoV-2, prior to the introduction of RSV vaccines. We analyzed data from primary care patients aged &#x2265;40 years with an acute respiratory infection. Between 02/10/2023 and 10/04/2024 virology swabs were tested by the UK Health Security Agency for RSV, influenza A and B, and SARS-CoV-2. Percent positivity with 95% confidence intervals (CIs) were estimated. Multivariable logistic regression identified predictors of infection. Clinical presentations were described and compared. Among 6,161 individuals tested, influenza A had the highest positivity (3.25%, 95% CI: 2.83-3.72), followed by SARS-CoV-2 (2.30%, 95% CI: 1.96-2.71), RSV (2.26%, 95% CI: 1.91-2.66), and influenza B (0.28%, 95% CI: 0.17-0.44). RSV positivity was higher in people aged 60-74 compared to those aged 40-49. RSV cases presented with ILI less often than COVID or influenza A cases. During the 2023/24 winter season in England, medically-attended RSV presented a significant disease burden, with a positivity comparable to SARS-CoV-2 and approximately 70% of influenza. Given well-established vaccination programmes for influenza and COVID-19, these findings demonstrate an opportunity to introduce an RSV vaccination programme for adults.

Understanding the burden of acute viral respiratory infection-related hospitalizations is crucial for guiding research and development. Unlike influenza, respiratory syncytial virus (RSV), or severe acute respiratory syndrome coronavirus 2, no pharmaceutical interventions exist for other respiratory viruses; therefore, their impact remains poorly characterized. This study aimed to investigate the association of current non-vaccine-preventable respiratory viruses, especially rhinovirus/enterovirus (RV/EV), on hospitalizations during the respiratory seasons. Data from a prospective study that used multiplex polymerase chain reaction to conduct long-term surveillance on respiratory viruses in Valencia, Spain were analyzed. Patients aged &#x2265;50 years hospitalized due to respiratory illness from 2014-15-2019-20 were included. Respiratory viruses were detected in 35.2% (3,755/10,675) of hospitalized patients with acute respiratory illness. Influenza and RSV accounted for 22.1% of hospitalizations, RV/EV for 7.6%, and other non-vaccine-preventable viruses for 5.4%. Adults &#x2265;75 years had average seasonal hospitalization incidence rates more than twice those aged 65-74 years and eight times those aged 50-64-year-olds. No significant differences in severity markers were observed among patients with or without virus identified, those aged &#x2265;75 years had a 2-3 times higher mortality rate compared to younger age groups. The potential impact of respiratory viruses on hospitalization rates among older adults, particularly those aged &#x2265;75 years, highlights the need for targeted interventions to reduce healthcare system burden. Enhanced diagnostic capabilities and the development of next-generation preventive strategies, including vaccines and therapeutics, could improve patient outcomes and strengthen the resilience of the healthcare system during respiratory virus seasons.

To estimate influenza vaccine effectiveness (VE) in the pediatric population (<18&#xa0;years) attending primary care in the European Union and European Economic Area in 2022/2023 and 2023/2024. General practitioners swabbed and interviewed patients with acute respiratory tract infection. We conducted a test-negative case-control study and used logistic regression to estimate VE against any influenza and specific (sub)types, overall and by age group, and within the vaccine recommendation target group. Among 10&#x2009;368 children in 2022/23, 3286 (32%) tested polymerase chain reaction-positive for influenza virus; among 9270 children in 2023/24, 1567 (17%) tested positive. Influenza A(H3N2) and B predominated in 2022/23, and influenza A(H1N1)pdm09 in 2023/24. Among the test-negative controls, 17% were part of the vaccine recommendation target group in 2022/23 and 38% in 2023/24. In 2022/23, overall VE against any influenza was 68% (95% CI: 59-76); 57% (95% CI: 26-76) against influenza A(H1N1)pdm09; 54% (95% CI: 33-69) against influenza A(H3N2); 83% (95% CI: 74-90) against influenza B. In 2023/24, overall VE against any influenza was 71% (95% CI: 62-78); 75% (95% CI: 64-83) against influenza A(H1N1)pdm09; 40% (95% CI: 4-64) against influenza A(H3N2); and 92% (95% CI: 63-100) against influenza B. All VE estimates varied by age and vaccine recommendation target group. In 2022/23 and 2023/24, more than two-thirds of vaccinated children were protected against primary care-attended influenza infection in Europe. Monitoring VE in children can help inform influenza immunization programs.

Respiratory viruses are common causes of upper and lower respiratory tract illness and can also result in hospitalization and death. CDC conducts national surveillance using multiple systems to monitor ongoing and seasonal changes in the activity of selected respiratory viruses. This report summarizes U.S. trends in endemic respiratory virus activity during July 2024-June 2025. For SARS-CoV-2 and respiratory syncytial virus (RSV), national and regional trends; population-based hospitalization rates; vital records death counts; and preliminary estimates of associated illnesses, outpatient visits, hospitalizations, and deaths are described, as well as genetic characterization of circulating SARS-CoV-2 viruses. Some viruses, including SARS-CoV-2, showed bimodal peaks in positive laboratory test results, whereas others, including RSV and influenza viruses, were characterized by a single peak. The highest COVID-19-associated hospitalization rates were reported among adults aged &#x2265;75 years (932.6 per 100,000 persons), infants aged <6 months (285.6), and adults aged 65-74 years (274.4). RSV-associated hospitalization rates were highest among infants aged <12 months (1,116.7 per 100,000; 95% CI&#xa0;=&#xa0;1,078.4-1,157.9), children aged 12-23 months (770.6; 95% CI&#xa0;=&#xa0;743.1-800.3), and adults aged &#x2265;75 years (426.9; 95% CI&#xa0;=&#xa0;366.6-510.8). COVID-19 was associated with an estimated 290,000-450,000 hospitalizations and 34,000-53,000 deaths; RSV was associated with 190,000-350,000 hospitalizations and 10,000-23,000 deaths. All circulating SARS-CoV-2 lineages were Omicron JN.1 descendants. Staying up to date with recommended COVID-19, RSV, and influenza vaccinations remains important to reducing the risk for severe disease caused by these viruses.

To investigate the detection rate of respiratory viruses identified by multiplex real-time PCR (MPL real-time PCR) in respiratory specimens collected from hospitalized patients with acute lower respiratory tract infections (LRTI) over a five-year period (2020-2024), and to emphasize the importance of MPL real-time PCR testing in identifying respiratory viruses responsible for severe lower respiratory tract infections requiring hospitalization. This cross-sectional retrospective study analyzed 15,936 respiratory specimens collected from hospitalized patients between 2020 and 2024. Seventeen respiratory viruses were detected using MPL real-time PCR. Statistical comparisons were performed using the chi-square test. The overall respiratory virus detection rate was 31.88% and was significantly higher in children than in adults (52.98% vs. 18.10%). The most frequently detected viruses were rhinovirus, influenza A, respiratory syncytial virus, and parainfluenza virus type 3, while influenza A and SARS-CoV-2 predominated in adults. During the peak of the COVID-19 pandemic in 2021, SARS-CoV-2 accounted for 78.92% of detected viruses, accompanied by marked suppression of other respiratory pathogens. Measles virus re-emerged in 2024, predominantly affecting children (17.65%). Most Respiratory virus-positive cases (82.8%) involved single-agent infections. Hospitalized acute LRTI cases often lack distinctive clinical signs to identify viral pathogens. MPL real-time PCR provides simultaneous multi-virus detection, enabling accurate etiological diagnosis and strengthening hospital-based viral surveillance, particularly in resource-limited settings.

Understanding the genetic changes that allow avian influenza A viruses (IAVs) to switch their natural hosts and establish productive infection in humans is important for pandemic risk assessment. Adaptations in the IAV polymerase are required to overcome species-specific restrictions imposed by host ANP32 proteins. Notably, avian virus polymerase is generally only poorly supported by human ANP32 proteins due to species-specific differences. Consequently, efficient polymerase adaptation to the binding interface of human ANP32 requires distinct amino acid changes, such as PB2 E627K. A separate adaptation, PB2 M631L, has recently been reported in mammalian-adapted IAV; however, its functional role across divergent viral lineages and its relationship to host ANP32-dependent adaptation remain incompletely defined. Here, we examine PB2 M631L in the polymerases of a 1918 pandemic strain, a recombinant contemporary H1N1pdm09, and a recent clade 2.3.4.4b H5N1 virus. Using polymerase activity and protein-interaction assays, we show that PB2 M631L enhances polymerase activity and ANP32 binding in human-but not avian-contexts, and that this effect is conserved across multiple viral backgrounds. In H1N1pdm09, PB2 M631L also increased virus replication in mammalian cells. These findings indicate that PB2 M631L contributes to enhanced polymerase compatibility with human ANP32 proteins and are consistent with a role in adaptation across multiple influenza virus lineages. Our results highlight how analysis of historical pandemic strains can inform risk assessment for future emerging viruses.

Genomic surveillance of human seasonal influenza viruses is an essential component of the Global Influenza Surveillance and Response system (GISRS) and informs the recommendations for the seasonal influenza vaccine composition. Phylogenetic analysis of viral genome sequences is used to identify groups of viruses sharing potential antigenic change, and computational models are used to predict which viral variants are likely to circulate at high levels in upcoming seasons. To facilitate discussion and reporting of genetic diversity, as well as to communicate antigen recommendations, up-to-date and sufficiently granular definitions of genetic clades are important. We implemented a nomenclature system for Segments 4 (haemagglutinin) and 6 (neuraminidase) of human Influenza A(H3N2), A(H1N1)pdm09, and Influenza B that dynamically adapts to the diversity of circulating viruses. New subclades were proposed by a clade suggestion algorithm based on criteria including (i) the number of sequences in the group, (ii) the distance from the direct parent clade, and (iii) the weighted number of amino acid substitutions on the branch leading to the common ancestor of the subclade. Algorithmic clade proposals were reviewed and assigned a systematic hierarchical label consisting of a leading letter, followed by numbers (e.g., G.1.3). Names are kept short by aliasing that is collapsing prefixes into unique letters. Subclade definitions are shared openly to promote adoption and tool development. Nextclade is supporting this new nomenclature, and it is being used routinely by the GISRS network. With increasing genomic surveillance, the need for up-to-date classification schemes is growing and we hope that the current dynamic proposal will adapt to growing data volumes and aid in simplifying the interpretation of these data.

In India, no publicly funded seasonal influenza immunization is ongoing, partly because cost-effectiveness is yet to be established. We estimate the cost-effectiveness and budgetary impact of introducing seasonal influenza vaccination among adults aged &#x2265;&#x2009;60&#x2009;years in India, a known high-risk group. Estimates of disease burden including disability adjusted life years (DALYs) were generated from 3-year community cohorts and hospital-based study set up at four sites to estimate incidence of symptomatic acute respiratory infections (ARI), health care utilization, costs and outcomes and applied to India's 2021 estimated population. We used a decision analysis model from an abridged societal perspective for implementation of an inactivated trivalent influenza vaccination programme for older adults (aged &#x2265;&#x2009;60&#x2009;years) using either facility-based or outreach-based approaches. We estimated incremental cost-effectiveness ratio (ICER) per DALY averted and used India's per capita gross domestic product of US$ 2238 for 2021 as the cost-effectiveness threshold. We performed deterministic and probabilistic sensitivity analyses. We also estimated ICER for immunizing all those above 65&#x2009;years or with comorbidities. Using financial cost of the vaccination programme and the direct medical cost of disease averted we estimated its budgetary impact. In 2021, older adults in India had 5.3 (95% CI: 3.6-7.7) million influenza-ARIs resulting in 36,149 (95% CI: 30,076-43,268) hospitalizations and 84,613 (95% CI: 39,895-155,454) deaths. It amounted to a total of 974,019 DALYs and US$ 66.6 million. As compared with no vaccination, facility-based and outreach-based influenza vaccination had an ICER of US$1979 and US$1851, respectively, below the cost-effectiveness threshold. In all sensitivity and scenario analyses, ICER estimates were below the threshold and vaccinating those above 60&#x2009;years with specified comorbidities using a passive approach was found to be most cost-effective with least budgetary impact. Annually vaccinating older adults against influenza was found to be cost-effective in the majority of scenarios considered in the study. Given the budgetary implication, it might be prudent to focus on those with co-morbidities.

Emergency department (ED) syndromic surveillance (EDSyS) often relies on preliminary or ED discharge diagnosis codes as indicators of influenza, but few studies provide a justification for their selection. This retrospective analytical study aimed to optimise the selection of diagnostic codes in EDSyS for monitoring influenza activity and severity. Diagnostic codes potentially relating to a respiratory infection and assigned to people presenting to over 180 EDs in New South Wales (NSW), Australia, were grouped into 16 mutually exclusive 'ED Syndromes'. Time series of the proportion of ED presentations for each ED syndrome by epidemiological week between 2010 and 2019 were compared to a reference series of the percentage influenza positive results from sentinel laboratories, using two similarity and three timeliness statistics. Hospital inpatient admission and laboratory notification data linked to each ED presentation allowed assessment of patient infection status and outcomes. 'Unspecified Viral' (any non-specific viral illness, without reference to the respiratory system) and ED syndromes based on influenza like Illness (ILI) and influenza had the best combination of similarity and timeliness measures. Linked data identified relatively high rates of hospital admission, laboratory-confirmed influenza and inpatient influenza diagnosis for ED syndromes based on pneumonia and lower respiratory tract infection. In addition to ILI and influenza, ED syndromes based on unspecified viral illnesses can be used for EDSyS to assess influenza timing and transmissibility in NSW, Australia. The approach outlined in our paper can identify diagnostic codes to improve severity assessment of seasonal influenza using EDSyS.