Seasonal Influenza Epidemics Research Articles

Hospitalizations and emergency attendance averted by influenza vaccination in Victoria, Australia, 2017 - 2019.

Seasonal influenza epidemics result in high levels of healthcare utilization. Vaccination is an effective strategy to reduce the influenza-related burden of disease. However, reporting vaccine effectiveness does not convey the population impacts of influenza vaccination. We aimed to calculate the burden of influenza-related hospitalizations and emergency department (ED) attendance averted by influenza vaccination in Victoria, Australia, from 2017 to 2019, and associated economic savings. We applied a compartmental model to hospitalizations and ED attendances with influenza-specific, and pneumonia and influenza (P&I) with the International Classification of Diseases, 10th Revision, Australian Modification (ICD-10-AM) diagnostic codes of J09-J11 and J09-J18, respectively. We estimated an annual average of 7657 (120 per 100000 population) hospitalizations and 20560 (322 per 100000 population) ED attendances over the study period, associated with A$85 million hospital expenditure. We estimated that influenza vaccination averted an annual average of 1182 [range: 556 - 2277] hospitalizations and 3286 [range: 1554 - 6257] ED attendances and reduced the demand for healthcare services at the influenza season peak. This equated to approximately A13 [range: A6 - A25] million of savings over the study period. Calculating the burden averted is feasible in Australia and auseful approach to demonstrate the health and economic benefits of influenza vaccination.

Molecular epidemiology and vaccine compatibility analysis of seasonal influenza A viruses in the context of COVID-19 epidemic in Wuhan, China.

The COVID-19 pandemic had a significant impact on the global influenza vaccination and the epidemics of seasonal influenza. To further explore the molecular epidemiology of influenza viruses and assess vaccine effectiveness, we collected influenza cases in Wuhan during the 2022-2023 influenza season. Among 1312 clinical samples, 312 samples tested positive for influenza viruses using reverse transcription polymerase chain reaction. These positive samples included 146A/H1N1 subtypes (46.8%), 164A/H3N2 subtypes (52.6%) and 2 influenza B virus types (0.6%). Based on the whole genome sequence information of hemagglutinin (HA) and neuraminidase (NA) from 27A/H1N1 influenza virus strains and 26A/H3N2 influenza virus strains obtained in this study, a phylogenetic analysis was conducted. The analysis revealed that all A/H1N1 strains belonged to the evolutionary branch 6B.1A.5a.2a, and they exhibited specific substitutions at positions K71Q, Q206E, E241A, and R276K. Similarly, all A/H3N2 strains were classified into the 3C.2a1b.2a.1a subclade and displayed amino acid substitutions at positions S172H, N175Y, I176T, K187N, and S214P. Notably, the A/H3N2 strains also acquired a new potential glycosylation site at position N174. Using an epitope model, the predicted vaccine effectiveness was assessed for the A/H1N1 and A/H3N2 strains. The predicted vaccine effectiveness against the Wuhan influenza epidemic strain was over 85% for the A/H1N1 vaccine strain. However, the effectiveness against the A/H3N2 vaccine strain was only 48.7%. To further verify the protection of influenza vaccine against circulating influenza viruses in the region, we conducted in vivo and in vitro animal studies. The results of in vitro neutralization experiment showed that rabbit serum antibodies inoculated with quadrivalent isolated influenza vaccine had neutralization ability against all 24 isolated influenza viruses. In vivo experiments showed that vaccinated mice had fewer lung lesions when infected with the influenza strain circulating in Wuhan, suggesting that vaccination can effectively reduce the occurrence of severe lung damage. These findings emphasize the importance of accurately predicting seasonal influenza strains for effective influenza prevention and control, especially during the co-circulation of SARS-CoV-2 and influenza viruses. This study provides valuable information on the seasonal influenza virus in Wuhan during the COVID-19 pandemic and serves as a basis for vaccine prediction and updates.

Influenza Vaccine Effectiveness and Progress Towards a Universal Influenza Vaccine.

At various times in recent decades, surges have occurred in optimism about the potential for universal influenza vaccines that provide strong, broad, and long-lasting protection and could substantially reduce the disease burden associated with seasonal influenza epidemics as well as the threat posed by pandemic influenza. Each year more than 500 million doses of seasonal influenza vaccine are administered around the world, with most doses being egg-grown inactivated subunit or split-virion vaccines. These vaccines tend to have moderate effectiveness against medically attended influenza for influenza A(H1N1) and influenza B, and somewhat lower for influenza A(H3N2) where differences between vaccine strains and circulating strains can occur more frequently due to antigenic drift and egg adaptations in the vaccine strains. Several enhanced influenza vaccine platforms have been developed including cell-grown antigen, the inclusion of adjuvants, or higher antigen doses, to improve immunogenicity and protection. During the COVID-19 pandemic there was unprecedented speed in development and roll-out of relatively new vaccine platforms, including mRNA vaccines and viral vector vaccines. These new platforms present opportunities to improve protection for influenza beyond existing products. Other approaches continue to be explored. Incremental improvements in influenza vaccine performance should be achievable in the short to medium term.

Forecasting influenza epidemics in China using transmission dynamic model with absolute humidity

BackgroundAn influenza forecasting system is critical to influenza epidemic preparedness. Low temperature has long been recognized as a condition favoring influenza epidemic, yet it fails to justify the summer influenza peak in tropics/subtropics. Recent studies have suggested that absolute humidity (AH) had a U-shape relationship with influenza survival and transmission across climate zones, indicating that a unified influenza forecasting system could be established for China with various climate conditions. MethodsOur study has generated weekly influenza forecasts by season and type/subtype in northern and southern China from 2011 to 2021, using a forecasting system combining an AH-driven susceptible-infected-recovered-susceptible (SIRS) model and the ensemble adjustment Kalman filter (EAKF). Model performance was assessed by sensitivity and specificity in predicting epidemics, and by accuracies in predicting peak timing and magnitude. ResultsOur forecast system can generally well predict seasonal influenza epidemics (mean sensitivity>87.5%; mean specificity >80%). The average forecast accuracies were 82% and 60% for peak timing and magnitude at 3–6 weeks ahead for northern China, higher than those of 42% and 20% for southern China. The accuracy was generally better when the forecast was made closer to the actual peak time. DiscussionThe established AH-driven forecasting system can generally well predict the occurrence of seasonal influenza epidemics in China.

The Development History, Structural Composition, and Functions of Influenza Viruses and the Progress of Influenza Virus Inhibitors in Clinics and Clinical Trials.

Flu is an acute respiratory disease caused by influenza viruses. The influenza viruses are classified as Alphainfluenzavirus (influenza A virus, IAV), Betainfluenzavirus (influenza B virus, IBV), Gammainfluenzavirus (influenza C virus, ICV), and Deltainfluenzavirus (influenza D virus, IDV) according to the antigenicity of nucleoproteins (NPs) and matrix (M) proteins in vivo. It is estimated that the seasonal influenza epidemics will cause about 3-5 million cases of serious illness and 290,000-650,000 deaths in the world every year, while influenza A virus is the leading cause of infection and death. Neuraminidase (NA) is one of the most critical targets for the development of anti-influenza virus drugs, and the main drugs clinically applied for the treatment of flu are neuraminidase inhibitors. However, various mutant strains have developed resistance to these inhibitors (For example, the substrains of H274Y in H1N1, H5N1, and E119V in H3N2 have developed resistance to Oseltamivir). Influenza viruses mutate frequently, and new substrains emerge constantly, and the pandemics caused by the new substrains will break out at any time. Therefore, it is urgent to develop new and wide-spectrum influenza virus inhibitors for overcoming the emerging influenza pandemic. Here, we focus on describing the progress of influenza virus inhibitors in clinics and clinical trials to provide a comprehensive reference for the researchers.

Evaluation of FluSight influenza forecasting in the 2021–22 and 2022–23 seasons with a new target laboratory-confirmed influenza hospitalizations

Accurate forecasts can enable more effective public health responses during seasonal influenza epidemics. For the 2021–22 and 2022–23 influenza seasons, 26 forecasting teams provided national and jurisdiction-specific probabilistic predictions of weekly confirmed influenza hospital admissions for one-to-four weeks ahead. Forecast skill is evaluated using the Weighted Interval Score (WIS), relative WIS, and coverage. Six out of 23 models outperform the baseline model across forecast weeks and locations in 2021–22 and 12 out of 18 models in 2022–23. Averaging across all forecast targets, the FluSight ensemble is the 2nd most accurate model measured by WIS in 2021–22 and the 5th most accurate in the 2022–23 season. Forecast skill and 95% coverage for the FluSight ensemble and most component models degrade over longer forecast horizons. In this work we demonstrate that while the FluSight ensemble was a robust predictor, even ensembles face challenges during periods of rapid change.

ATAGI targeted review 2023: Vaccination for preventing influenza in Australia.

Annual seasonal influenza epidemics cause substantial disease and economic burden worldwide. During the coronavirus disease 2019 (COVID-19) pandemic in 2020 and 2021, influenza activity significantly declined. However, influenza resurged in Australia following the relaxation of non-pharmaceutical interventions, with increased influenza virus circulation in early 2022 coinciding with the SARS-CoV-2 Omicron BA.2 variant wave. Together with other respiratory virus diseases, these disease impacts on the Australian population and healthcare system have re-emphasised the importance of influenza vaccination and control. We aim to provide an overview of the current seasonal influenza vaccination program in Australia and summarise evidence and considerations underpinning potential future immunisation strategies. Influenza causes disproportionately higher morbidity and mortality in young children and older adults. Other populations at elevated risk from influenza include Aboriginal and Torres Strait Islander peoples, pregnant women, and people with certain underlying medical conditions. All Australians aged ≥ 6 months are recommended to receive influenza vaccine every year. The National Immunisation Program (NIP) provides free vaccine for eligible at-risk populations. While approximately 70% of older adults had received influenza vaccine in 2022, coverage in other age groups remains suboptimal. There are several key unmet needs and challenges, but also potential strategies for enhancing the influenza vaccination program in Australia. Improved monitoring and evaluation, including the use of relevant linked datasets for such purposes, is imperative to better understand variations in coverage and vaccination impact in specific populations. Adoption of evidence-based strategies, such as culturally appropriate resources that consider the characteristics of diverse Australian populations, may also help to achieve higher vaccine coverage rates. Additionally, greater vaccine uptake across the population could be facilitated by expanding the NIP-eligible population where cost-effective, and adopting the use of more effective and different types of vaccines when available.

Effect of Social Distancing Caused by Heavy Snowfall on Seasonal Influenza Epidemic in a Local Region in Japan.

The effectiveness of social distancing in controlling influenza epidemics is debatable. We analyzed the local impact of large-scale social distancing caused by heavy snowfall on influenza epidemic. Surveillance data from the National Institute of Infectious Diseases on influenza diagnosed at registered Fukui Prefecture institutions were plotted in epidemic curves. We also compared the number of elementary and junior high school students suspended attendance due to influenza during the 2017/2018 season between the northern and southern Fukui Prefecture territories. Weekly incidence influenza rates and average rates before, during and after school closure caused by heavy snowfall in the northern territory were compared with those of the southern territory using Poisson generalized estimating equations to account for school variability. The northern territory epidemic curve, like the nationwide trend, rapidly declined during the heavy snowfall and formed a second peak 4 weeks later. The southern territory's curve was like the nationwide trend throughout. Weekly incidence rate ratios in schools for the northern versus southern territories varied from 0.23 during heavy snowfall to 2.32, 4 weeks after the snowfall. Cumulative incidence ratio (95% confidence interval) of the northern-to-southern territories was 0.92 (0.74-1.13; P = 0.42). School closure significantly reduced the incidence rate to 0.41 (95% confidence interval, 0.19-0.89; P = 0.02). Although relatively large-scale, simultaneous school closures and social distancing could temporarily suppress seasonal influenza epidemic, they could not impede the cumulative incidence. Large-scale social distancing may contribute to slowing infection spread during seasonal influenza epidemics.

Nasal irrigation during seasonal epidemics of influenza and acute respiratory viral infections

Nasal irrigation during seasonal epidemics of influenza and acute respiratory viral infections

Cross-protective efficacy and safety of an adenovirus-based universal influenza vaccine expressing nucleoprotein, hemagglutinin, and the ectodomain of matrix protein 2

It is necessary to develop universal vaccines that act broadly and continuously to combat regular seasonal epidemics of influenza and rare pandemics. The aim of this study was to find the optimal dose regimen for the efficacy and safety of a mixture of previously developed recombinant adenovirus-based vaccines that expressed influenza nucleoprotein, hemagglutinin, and ectodomain of matrix protein 2 (rAd/NP and rAd/HA-M2e). The vaccine efficacy and safety were measured in the immunized mice with the mixture of rAd/NP and rAd/HA-M2e intranasally or intramuscularly. The minimum dose that would be efficacious in a single intranasal administration of the vaccine mixture and cross-protective efficacy against various influenza strains were examined. In addition, the immune responses that may affect the cross-protective efficacy were measured. We found that intranasal administration is an optimal route for 107 pfu of vaccine mixture, which is effective against pre-existing immunity against adenovirus. In a study to find the minimum dose with vaccine efficacy, the 106 pfu of vaccine mixture showed higher antibody titers to the nucleoprotein than did the same dose of rAd/NP alone in the serum of immunized mice. The 106 pfu of vaccine mixture overcame the morbidity and mortality of mice against the lethal dose of pH1N1, H3N2, and H5N1 influenza infections. No noticeable side effects were observed in single and repeated toxicity studies. We found that the mucosal administration of adenovirus-based universal influenza vaccine has both efficacy and safety, and can provide cross-protection against various influenza infections even at doses lower than those previously known to be effective.

Do all Emergency Room Patients With Influenza-like Symptoms Need Blood Cultures? A Retrospective Cohort Study of 2 Annual Influenza Seasons.

In this retrospective cohort study, we evaluated risk factors for bacteremia in emergency department patients presenting with influenza-like symptoms during influenza epidemic seasons. In patients without fever, chronic heart or chronic liver disease, blood culture collection might be omitted.

Bioinformatics and system biology approach to identify the influences among COVID-19, influenza, and HIV on the regulation of gene expression.

Coronavirus disease (COVID-19), caused by SARS-CoV-2, has emerged as a infectious disease, coexisting with widespread seasonal and sporadic influenza epidemics globally. Individuals living with HIV, characterized by compromised immune systems, face an elevated risk of severe outcomes and increased mortality when affected by COVID-19. Despite this connection, the molecular intricacies linking COVID-19, influenza, and HIV remain unclear. Our research endeavors to elucidate the shared pathways and molecular markers in individuals with HIV concurrently infected with COVID-19 and influenza. Furthermore, we aim to identify potential medications that may prove beneficial in managing these three interconnected illnesses. Sequencing data for COVID-19 (GSE157103), influenza (GSE185576), and HIV (GSE195434) were retrieved from the GEO database. Commonly expressed differentially expressed genes (DEGs) were identified across the three datasets, followed by immune infiltration analysis and diagnostic ROC analysis on the DEGs. Functional enrichment analysis was performed using GO/KEGG and Gene Set Enrichment Analysis (GSEA). Hub genes were screened through a Protein-Protein Interaction networks (PPIs) analysis among DEGs. Analysis of miRNAs, transcription factors, drug chemicals, diseases, and RNA-binding proteins was conducted based on the identified hub genes. Finally, quantitative PCR (qPCR) expression verification was undertaken for selected hub genes. The analysis of the three datasets revealed a total of 22 shared DEGs, with the majority exhibiting an area under the curve value exceeding 0.7. Functional enrichment analysis with GO/KEGG and GSEA primarily highlighted signaling pathways associated with ribosomes and tumors. The ten identified hub genes included IFI44L, IFI44, RSAD2, ISG15, IFIT3, OAS1, EIF2AK2, IFI27, OASL, and EPSTI1. Additionally, five crucial miRNAs (hsa-miR-8060, hsa-miR-6890-5p, hsa-miR-5003-3p, hsa-miR-6893-3p, and hsa-miR-6069), five essential transcription factors (CREB1, CEBPB, EGR1, EP300, and IRF1), and the top ten significant drug chemicals (estradiol, progesterone, tretinoin, calcitriol, fluorouracil, methotrexate, lipopolysaccharide, valproic acid, silicon dioxide, cyclosporine) were identified. This research provides valuable insights into shared molecular targets, signaling pathways, drug chemicals, and potential biomarkers for individuals facing the complex intersection of COVID-19, influenza, and HIV. These findings hold promise for enhancing the precision of diagnosis and treatment for individuals with HIV co-infected with COVID-19 and influenza.

Progress of Influenza Viruses and Inhibitors.

Influenza is an acute respiratory disease caused by influenza viruses. It has the characteristics of fast transmission and strong infectivity, and it does great harm to human health and survival. It is estimated that the seasonal influenza epidemics every year will cause about one billion cases of infections and hundreds of thousands of deaths worldwide, while influenza A virus is the leading cause of infection and death. Currently, the main drugs used in clinics to treat influenza viruses are neuraminidase inhibitors, and these drugs have shown excellent efficacy in treating influenza viruses. However, various mutant strains have developed resistance to these effective drugs in clinics (such as the subtype mutant strains of H274Y in H1N1 or H5N1 and E119V in H3N2 have developed resistance to Oseltamivir). Influenza viruses mutate frequently, and new viral strains are constantly discovered, and the pandemics will break out at any time. Therefore, it is urgent to develop efficient and broad-spectrum drugs to prevent and treat the influenza pandemic caused by the emerging new subtypes. This review focuses on describing the pandemic history, the structure, function and prevention methods of influenza viruses and the progress of the development of anti-influenza drugs, to provide the reference for prevention and treatment of influenza viruses and development of influenza virus inhibitors.

Month-to-month all-cause mortality forecasting: a method allowing for changes in seasonal patterns.

Forecasting of seasonal mortality patterns can provide useful information for planning health-care demand and capacity. Timely mortality forecasts are needed during severe winter spikes and/or pandemic waves to guide policy-making and public health decisions. In this article, we propose a flexible method for forecasting all-cause mortality in real time considering short-term changes in seasonal patterns within an epidemiologic year. All-cause mortality data have the advantage of being available with less delay than cause-specific mortality data. In this study, we use all-cause monthly death counts obtained from the national statistical offices of Denmark, France, Spain, and Sweden from epidemic seasons 2012-2013 through 2021-2022 to demonstrate the performance of the proposed approach. The method forecasts deaths 1 month ahead, based on their expected ratio to the next month. Prediction intervals are obtained via bootstrapping. The forecasts accurately predict the winter mortality peaks before the COVID-19 pandemic. Although the method predicts mortality less accurately during the first wave of the COVID-19 pandemic, it captures the aspects of later waves better than other traditional methods. The method is attractive for health researchers and governmental offices for aiding public health responses because it uses minimal input data, makes simple and intuitive assumptions, and provides accurate forecasts both during seasonal influenza epidemics and during novel virus pandemics.

Does a Digital Health Application Could Be the Supplement to the Influenza Surveillance System?

Epidemics of seasonal influenza is a major public health concern in china. Historical percentage of influenza-like illness (ILI%) from CDC and health enquiry data from a health-related application were collected, when combining the real-time ILI-related search queries with one-week ago's ILI%, it was able to predict the trend of ILI correctly and timely. Digital health application is potentializing a supplement to the traditional influenza surveillance systems in China.

Trends in Anti-Influenza Drug Prescription and Adverse Drug Reaction Reporting After the Lifting of Oseltamivir Prescribing Restrictions in Pediatric Outpatients: An Ecological Study Using the MDV Analyzer® And the Japanese Adverse Drug Event Report Database.

Abnormal behavior after oseltamivir administration has been reported in the media; in 2007, the package insert for oseltamivir phosphate was revised to restrict its administration to individuals aged over 10 years. However, in 2018, the age limitation specified in the package insert was removed. Here, we evaluated the trends in anti-influenza drug prescription and adverse drug reactions (ADRs) reported in pediatric outpatients after revising the oseltamivir package insert as an ecological study. Anti-influenza drug prescriptions for pediatric outpatients with influenza aged 0-19 years were downloaded from the acute Diagnosis Procedure Combination hospital databases using the MDV analyzer®. ADR reports on anti-influenza drug prescription among patients aged 0-20 years in the Japanese Adverse Drug Event Report database were downloaded from the Pharmaceutical and Medical Devices Agency website. Data were collected during the 2016/2017 and 2019/2020 influenza seasons. During the influenza epidemic season (January-March), the percentage of oseltamivir prescriptions for patients with influenza aged 10-19 years tripled after the revision of the oseltamivir package insert (9.3% during the 2016/2017 season and 29.2% during the 2019/2020 season); however, reports of abnormal behavior did not increase (two during the 2016/2017 season and none during the 2019/2020 season). The number of oseltamivir-related ADR reports among minors over 10 years of age did not increase although the proportion of oseltamivir prescriptions increased after the revision of the oseltamivir package insert.

Determinants of epidemic size and the impacts of lulls in seasonal influenza virus circulation

During the COVID-19 pandemic, levels of seasonal influenza virus circulation were unprecedentedly low, leading to concerns that a lack of exposure to influenza viruses, combined with waning antibody titres, could result in larger and/or more severe post-pandemic seasonal influenza epidemics. However, in most countries the first post-pandemic influenza season was not unusually large and/or severe. Here, based on an analysis of historical influenza virus epidemic patterns from 2002 to 2019, we show that historic lulls in influenza virus circulation had relatively minor impacts on subsequent epidemic size and that epidemic size was more substantially impacted by season-specific effects unrelated to the magnitude of circulation in prior seasons. From measurements of antibody levels from serum samples collected each year from 2017 to 2021, we show that the rate of waning of antibody titres against influenza virus during the pandemic was smaller than assumed in predictive models. Taken together, these results partially explain why the re-emergence of seasonal influenza virus epidemics was less dramatic than anticipated and suggest that influenza virus epidemic dynamics are not currently amenable to multi-season prediction.

Epidemiological features of seasonal influenza transmission among 11 climate zones in Chinese Mainland

BackgroundPrevious studies provided some evidence of meteorological factors influence seasonal influenza transmission patterns varying across regions and latitudes. However, research on seasonal influenza activities based on climate zones are still in lack. This study aims to utilize the ecological-based Köppen Geiger climate zones classification system to compare the spatial and temporal epidemiological characteristics of seasonal influenza in Chinese Mainland and assess the feasibility of developing an early warning system.MethodsWeekly influenza cases number from 2014 to 2019 at the county and city level were sourced from China National Notifiable Infectious Disease Report Information System. Epidemic temporal indices, time series seasonality decomposition, spatial modelling theories including Moran’s I and local indicators of spatial association were applied to identify the spatial and temporal patterns of influenza transmission.ResultsAll climate zones had peaks in Winter-Spring season. Arid, desert, cold (BWk) showed up the first peak. Only Tropical, savannah (Aw) and Temperate, dry winter with hot summer (Cwa) zones had unique summer peak. Temperate, no dry season and hot summer (Cfa) zone had highest average incidence rate (IR) at 1.047/100,000. The Global Moran’s I showed that average IR had significant clustered trend (z = 53.69, P < 0.001), with local Moran’s I identified high-high cluster in Cfa and Cwa. IR differed among three age groups between climate zones (0–14 years old: F = 26.80, P < 0.001; 15–64 years old: F = 25.04, P < 0.001; Above 65 years old: F = 5.27, P < 0.001). Age group 0–14 years had highest average IR in Cwa and Cfa (IR = 6.23 and 6.21) with unique dual peaks in winter and spring season showed by seasonality decomposition.ConclusionsSeasonal influenza exhibited distinct spatial and temporal patterns in different climate zones. Seasonal influenza primarily emerged in BWk, subsequently in Cfa and Cwa. Cfa, Cwa and BSk pose high risk for seasonal influenza epidemics. The research finds will provide scientific evidence for developing seasonal influenza early warning system based on climate zones.

Russian Short-Term Mortality Fluctuations Data Series

The COVID-19 pandemic has revealed significant gaps in the coverage and quality of the existing international and national statistical surveillance systems. The most reliable approach to estimating mortality associated with short-term risk factors or factors fluctuating within calendar years is based on estimating weekly excess mortality. Although this approach is obvious, its application turned out to be problematic due to the lack of reliable data. In response to this challenge, a new Short-Term Mortality Fluctuations (STMF) data series was created in 2020. The Russian Short-Term Mortality Fluctuations Data Series (RuSTMF) is a further development of the STMF idea at the regional level. It contains weekly crude and standardized death rates for the Russian regions and Russia as a whole. The main source for calculating death rates is depersonalized individual data on the deceased provided by the Rosstat. This database provides for the analysis of short- and medium-term changes in mortality in males, females and total population in Russia as a whole and its regions, as well as the estimation of «excess» deaths during short-term sharp increases in mortality due to, for example, heat or cold waves, seasonal influenza epidemics, the Covid-19 pandemic or technogenic catastrophes.

Rapid detection of human influenza A viruses by HFman probe-based loop-mediated isothermal amplification assays

Since China abandoned the zero-COVID policy at the end of 2022, a wave of severe Flu pandemic emerged in China. Rapid and accurate diagnosis of Influenza A virus (IAV) is critical for clinical management and therapeutic decision-making of patients with fever. Here, we reported a novel IAV HF-LAMP assay, which can be performed with purified RNA or directly using clinical samples. The assays with purified RNA and clinical samples have high sensitivity with limit of detection (LOD) of 9.6 copies/reaction, 9900 copies/mL, and short sample-to-answer times of 36 and 50 min, respectively. Both assays showed high specificity and significantly higher IAV detection rate than the rapid antigen detection (RAD) assays. Furthermore, we found the vast majority (91.2 %) of children with fever during the pandemic were infected by IAV, and current IAV infection has a very narrow detectable window. The novel IVA HF-LAMP assays will provide robust tools to facilitate early diagnosis of IAV infection in current and future seasonal influenza epidemics.