Circulating Influenza Viruses Research Articles

Epidemic influenza virus nucleoprotein gene incorporated into vaccine influenza virus strain genome to optimize systemic and local T-cell immune response against live attenuated influenza vaccine

Introduction. Optimization of the vaccine-induced T-cell repertoire is one of the strategies to expand the spectrum of protective potential for live attenuated influenza vaccine (LAIV). LAIV cross-protective properties can be improved by introducing the nucleoprotein (NP) gene derived from epidemic parental virus into vaccine strain genome, i.e. by replacing the classical 6:2 genome formula with 5:3. The main objective of the present study was to detail evaluation for virus-specific systemic and tissue-resident memory T-cells subsets in mice immunized with seasonal H1N1 LAIV of the genome formula 6:2 and 5:3. Materials and methods. Two H1N1 LAIV strains with varying NP genes (LAIV 6:2 and LAIV 5:3) were generated using reverse genetics techniques. C57BL/6J mice were immunized intranasally with the vaccine candidates, twice, 3 weeks apart. Cells from the spleen and lung tissues were isolated 7 days after booster immunization to be stimulated with whole H1N1 influenza virus for assessing cytokine-producing memory CD44+CD62L– T-cells as well as expression of CD69 and CD103 surface markers using flow cytometry. Humoral murine serum immunity against H1N1 virus was assessed by ELISA. Results. The LAIV 5:3 vs classical 6:2 vaccine strain carrying the epidemic parental NP gene induced significantly more pronounced humoral immune response against recent influenza virus. The group of mice immunized with LAIV 5:3 demonstrated higher levels of virus-specific CD4+ and CD8+ effector memory T cells (TEM) in the spleen, including a subset of polyfunctional (IFNγ+TNFα+IL-2+) CD4+ TEM, compared to LAIV 6:2 group. Virus-specific memory T cell levels in lung tissues after immunization with LAIV 5:3 vs LAIV 6:2 also tended to increase, but no significant difference in stimulated tissue-resident CD69+CD103– and CD69+CD103+ T cells between the groups were found. Conclusion. Modification of the seasonal LAIV strain genome for updating its epitope composition allowed to enhance the virus-specific T-cell immune response both at systemic level and in lung tissues, thereby shoeing that the effectiveness of the vaccine against circulating influenza viruses can be potentially increased.

Amplification of avian influenza virus circulation along poultry marketing chains in Bangladesh: A controlled field experiment

The prevalence of avian influenza viruses is commonly found to increase dramatically as birds are transported from farms to live bird markets. Viral transmission dynamics along marketing chains are, however, poorly understood. To address this gap, we implemented a controlled field experiment altering chicken supply to a live bird market in Chattogram, Bangladesh. Broilers and backyard chickens traded along altered (intervention) and conventional (control) marketing chains were tested for avian influenza viruses at different time points. Upon arrival at the live bird market, the odds of detecting avian influenza viruses did not differ between control and intervention groups. However, 12 h later, intervention group odds were lower, particularly for broilers, indicating that viral shedding in live bird markets resulted partly from infections occurring during transport and trade. Curtailing avian influenza virus prevalence in live bird markets requires mitigating risk in marketing chain nodes preceding chickens’ delivery at live bird markets.

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.

Increase of Synergistic Secondary Antiviral Mutations in the Evolution of A(H1N1)pdm09 Influenza Virus Neuraminidases.

The unexpected emergence of oseltamivir-resistant A(H1N1) viruses in 2008 was facilitated in part by the establishment of permissive secondary neuraminidase (NA) substitutions that compensated for the fitness loss due to the NA-H275Y resistance substitution. These viruses were replaced in 2009 by oseltamivir-susceptible A(H1N1)pdm09 influenza viruses. Genetic analysis and screening of A(H1N1)pdm09 viruses circulating in Germany between 2009 and 2024 were conducted to identify any potentially synergistic or resistance-associated NA substitutions. Selected viruses were then subjected to further characterization in vitro. In the NA gene of circulating A(H1N1)pdm09 viruses, two secondary substitutions, NA-V241I and NA-N369K, were identified. These substitutions demonstrated a stable lineage in phylogenetic analysis since the 2010-2011 influenza season. The data indicate a slight increase in viral NA bearing two additional potentially synergistic substitutions, NA-I223V and NA-S247N, in the 2023-2024 season, which both result in a slight reduction in susceptibility to NA inhibitors. The accumulation of secondary synergistic substitutions in the NA of A(H1N1)pdm09 viruses increases the probability of the emergence of antiviral-resistant viruses. Therefore, it is crucial to closely monitor the evolution of circulating influenza viruses and to develop additional antiviral drugs against different target proteins.

Age, comorbidity burden and late presentation are significant predictors of hospitalization length and acute respiratory failure in patients with influenza

Influenza viruses are responsible for a high number of infections and hospitalizations every year. In this study, we aimed to identify clinical and host-specific factors that influence the duration of hospitalization and the progression to acute respiratory failure (ARF) in influenza. We performed an analysis of data from a prospective active influenza surveillance study that was conducted over five seasons (2018/19 to 2022/23). A total of 1402 patients with influenza were included in the analysis, the majority of which (64.5%) were children (under 18 years), and 9.1% were elderly. At least one chronic condition was present in 29.2% of patients, and 9.9% of patients developed ARF. The median hospital stay was 4 days (IQR: 3, 6 days). The most important predictors of prolonged hospital stay and development of ARF were extremes of age (infants and elderly), presence of chronic diseases, particularly the cumulus of at least 3 chronic diseases, and late presentation to hospital. Among the chronic diseases, chronic obstructive pulmonary disease, cardiovascular disease, cancer, diabetes, obesity, and chronic kidney disease were strongly associated with a longer duration of hospitalization and occurrence of ARF. In this context, interventions aimed at chronic disease management, promoting influenza vaccination, and improving awareness and access to health services may contribute to reducing the impact of influenza not only in Romania but globally. In addition, continued monitoring of the circulation of influenza viruses is essential to limit their spread among vulnerable populations.

Influenza virus circulation and vaccine effectiveness during June 2021–May 2023 in Thailand

Thai Ministry of Public Health recommends influenza vaccination for certain risk groups. We evaluated 2023 Southern Hemisphere influenza vaccine effectiveness against medically attended influenza using surveillance data from nine Thai hospitals and a test-negative design. During June 2022–May 2023, influenza vaccine provided moderate protection against seeking care for influenza illness (adjusted vaccine effectiveness 51%; 95% confidence interval 28–67). Understanding vaccine effectiveness can help guide future antigen selection and support clinicians to make a strong influenza vaccine recommendation to patients.

Global antigenic landscape and vaccine recommendation strategy for low pathogenic avian influenza A (H9N2) viruses

The sustained circulation of H9N2 avian influenza viruses (AIVs) poses a significant threat for contributing to a new pandemic. Given the temporal and spatial uncertainty in theantigenicity of H9N2 AIVs, the immune protection efficiency of vaccines remains challenging. By developing an antigenicity prediction method for H9N2 AIVs, named PREDAC-H9, the global antigenic landscape of H9N2 AIVs was mapped. PREDAC-H9 utilizes the XGBoost model with 14 well-designed features. The XGBoost model was built and evaluated to predict the antigenic relationship between any two viruses with high values of 81.1%, 81.4%, 81.3%, 81.1%, and 89.4% in accuracy, precision, recall, F1 value, and area under curve (AUC), respectively. Then the antigenic correlation network (ACnet) was constructed based on the predicted antigenic relationship for H9N2 AIVs from 1966 to 2022, and ten major antigenic clusters were identified. Of these, four novel clusters were generated in China in the past decade, demonstrating the unique complex situation there. To help tackle this situation, we applied PREDAC-H9 to calculate the cluster-transition determining sites and screen out virus strains with thehigh cross-protective spectrum, thus providing aninsilico reference for vaccine recommendation. The proposed model will reduce the clinical monitoring workload and provide a useful tool for surveillance and control of H9N2 AIVs.

COVID-19 restrictions limit the circulation of H3N2 canine influenza virus in China

Canine health is consistently affected by the circulation of the H3N2 strain of canine influenza virus (CIV). Prior research has indicated that the isolation rate of H3N2 CIVs in dogs has gradually increased in China, and these viruses have progressively adapted to humans over the course of their evolution within canine hosts, posing a significant public health threat. However, the key factors influencing the spread of CIVs remain elusive. From January 2020 to December 2022, during the COVID-19 pandemic, strict epidemic prevention policies were implemented in China. Thus, this measure provides an ideal model for studying factors influencing the prevalence of CIVs. In this study, we continuously monitored the prevalence of CIVs in China before and after the COVID-19 pandemic. We found that the pathogen detection rate and seropositivity rate of domestic CIVs significantly declined after the implementation of epidemic control measures. However, after restrictions on human movement were lifted in 2023, the circulation of CIVs gradually increased. Our results demonstrate that restricting human activity directly impacts the epidemic caused by CIVs and provide a theoretical basis for the implementation of control measures during outbreaks of zoonotic diseases in human companion animals.

Large-Scale Serological Survey of Influenza A Virus in South Korean Wild Boar (Sus scrofa).

In this comprehensive large-scale study, conducted from 2015 to 2019, 7,209 wild boars across South Korea were sampled to assess their exposure to influenza A viruses (IAVs). Of these, 250 (3.5%) were found to be IAV-positive by ELISA, and 150 (2.1%) by the hemagglutination inhibition test. Detected subtypes included 23 cases of pandemic 2009 H1N1, six of human seasonal H3N2, three of classical swine H1N1, 13 of triple-reassortant swine H1N2, seven of triple-reassortant swine H3N2, and seven of swine-origin H3N2 variant. Notably, none of the serum samples tested positive for avian IAV subtypes H3N8, H5N3, H7N7, and H9N2 or canine IAV subtype H3N2. This serologic analysis confirmed the exposure of Korean wild boars to various subtypes of swine and human influenza viruses, with some serum samples cross-reacting between swine and human strains, indicating potential infections with multiple IAVs. The results highlight the potential of wild boar as a novel mixing vessel, facilitating the adaptation of IAVs and their spillover to other hosts, including humans. In light of these findings, we recommend regular and frequent surveillance of circulating influenza viruses in the wild boar population as a proactive measure to prevent potential human influenza pandemics and wild boar influenza epizootics.

Effect of Nonpharmaceutical Interventions in Preventing COVID-19 on the Circulation of Avian Influenza Virus in Wuhan, Hubei Province, China

Background. In late 2019, several medical institutions in Wuhan, Hubei Province, China, reported cases of unexplained pneumonia. A novel coronavirus was isolated from human airway epithelial cells causing coronavirus disease-2019 (COVID-19). In recent years, many nonpharmaceutical interventions (NPIs) have been implemented to stop COVID-19 epidemic. This study aimed to explore the effect of NPIs on the circulation of avian influenza virus (AIV) in Wuhan. Materials and Methods. External environmental samples were collected and subjected to viral RNA extraction. Real-time quantitative polymerase chain reaction was used to detect the H5, H7, and H9 subtypes of AIV. Statistical analyses were performed using the chi-square test and binary logistic regression in SPSS 20.0 software. Results. A total of 2,451 external environmental samples were collected from seven districts from 2018 to 2022 in Wuhan, comprising 1,041 samples collected before COVID-19 and 1,410 samples after COVID-19. After COVID-19, the positive rate of AIV decreased significantly with the implementation of NPIs. The dominant subtype was the H9 subtype, followed by the H5 subtype. The positive rates of AIV in live poultry markets and poultry free-range sites were reduced significantly through the implementation of NPIs. Among the different sample types, higher positive rates of AIV were found in chopping boards, sewage, and cages. The positive rate of AIV was higher in trafficked source samples than that in autotrophic source samples. Conclusions. This study identified the characteristics of AIV in terms of different districts, surveillance sites, sample types, and bird sources in Wuhan. This study conducted a multifactorial analysis of the factors affecting AIV infection and provided a theoretical basis and guidance for the future prevention and control of AIV in Wuhan.

Detection of Novel Influenza Viruses Through Community and Healthcare Testing: Implications for Surveillance Efforts in the United States.

Novel influenza viruses pose a potential pandemic risk, and rapid detection of infections in humans is critical to characterizing the virus and facilitating the implementation of public health response measures. We use a probabilistic framework to estimate the likelihood that novel influenza virus cases would be detected through testing in different community and healthcare settings (urgent care, emergency department, hospital, and intensive care unit [ICU]) while at low frequencies in the United States. Parameters were informed by data on seasonal influenza virus activity and existing testing practices. In a baseline scenario reflecting the presence of 100 novel virus infections with similar severity to seasonal influenza viruses, the median probability of detecting at least one infection per month was highest in urgent care settings (72%) and when community testing was conducted at random among the general population (77%). However, urgent care testing was over 15 times more efficient (estimated as the number of cases detected per 100,000 tests) due to the larger number of tests required for community testing. In scenarios that assumed increased clinical severity of novel virus infection, median detection probabilities increased across all healthcare settings, particularly in hospitals and ICUs (up to 100%) where testing also became more efficient. Our results suggest that novel influenza virus circulation is likely to be detected through existing healthcare surveillance, with the most efficient testing setting impacted by the disease severity profile. These analyses can help inform future testing strategies to maximize the likelihood of novel influenza detection.

Relative Vaccine Effectiveness of Cell- vs Egg-Based Quadrivalent Influenza Vaccine Against Test-Confirmed Influenza Over 3 Seasons Between 2017 and 2020 in the United States.

Influenza vaccine viruses grown in eggs may acquire egg-adaptive mutations that may reduce antigenic similarity between vaccine and circulating influenza viruses and decrease vaccine effectiveness. We compared cell- and egg-based quadrivalent influenza vaccines (QIVc and QIVe, respectively) for preventing test-confirmed influenza over 3 US influenza seasons (2017-2020). Using a retrospective test-negative design, we estimated the relative vaccine effectiveness (rVE) of QIVc vs QIVe among individuals aged 4 to 64 years who had an acute respiratory or febrile illness and were tested for influenza in routine outpatient care. Exposure, outcome, and covariate data were obtained from electronic health records linked to pharmacy and medical claims. Season-specific rVE was estimated by comparing the odds of testing positive for influenza among QIVc vs QIVe recipients. Models were adjusted for age, sex, geographic region, influenza test date, and additional unbalanced covariates. A doubly robust approach was used combining inverse probability of treatment weights with multivariable regression. The study included 31 824, 33 388, and 34 398 patients in the 2017-2018, 2018-2019, and 2019-2020 seasons, respectively; ∼10% received QIVc and ∼90% received QIVe. QIVc demonstrated superior effectiveness vs QIVe in prevention of test-confirmed influenza: rVEs were 14.8% (95% CI, 7.0%-22.0%) in 2017-2018, 12.5% (95% CI, 4.7%-19.6%) in 2018-2019, and 10.0% (95% CI, 2.7%-16.7%) in 2019-2020. This study demonstrated consistently superior effectiveness of QIVc vs QIVe in preventing test-confirmed influenza over 3 seasons characterized by different circulating viruses and degrees of egg adaptation.

Real-life experience on COVID-19 and seasonal influenza vaccines co-administration in the vaccination hub of the University Hospital of Palermo, Italy

ABSTRACT With the pandemic, there has been a global reduction in influenza virus circulation, with WHO reporting, during 2021/22 season, laboratory testing positivity rate for influenza of less than 3%. Influenza surveillance systems anticipated a peak of influenza cases in the Northern Hemisphere during 2022/2023 season and the Italian Ministry of Health recommended the routinary co-administration of influenza with bivalent COVID-19 vaccines for the 2022/2023 season. At the Vaccination Hub of the University Hospital (UH) of Palermo, more than 700 subjects received influenza and COVID-19 booster doses in co-administration, during the 2021/2022 season. A cross-sectional study analyzing attitudes and factors associated with adherence to influenza and COVID-19 seasonal vaccines co-administration was conducted at the Vaccination Hub of the UH of Palermo, from October to December 2022. Among the 1,263 respondents, 74.7% (n = 944) received the co-administration of seasonal influenza and COVID-19 vaccines. The main reason reported for accepting it was confidence in the recommendations of the Health Ministry (41.3%). At the multivariable analysis, subjects aged ≤ 59 y old (AdjOR: 2.48; CIs95%: 1.89–3.65), male (AdjOR: 1.51; CIs95%: 1.27–1.75), Health-care professionals (HCPs) (AdjOR: 1.66; CIs95%: 1.08–2.57) and those who received co-administration during 2021/2022 (AdjOR: 41.6; CIs95%: 25.5–67.9) were significantly more prone to receive co-administration during 2022/23 season. From data obtained, the role of HCPs in accepting and then promoting co-administration of COVID-19 and influenza vaccines is crucial, as well as receiving co-administration in the previous season that represented the main drive for accepting it in the following seasons, supporting safety and effectiveness of this procedure.

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

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. 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. 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. 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.

Immunogenicity and protective efficacy of a co-formulated two-in-one inactivated whole virus particle COVID-19/influenza vaccine

Due to the synchronous circulation of seasonal influenza viruses and severe acute respiratory coronavirus 2 (SARS-CoV-2) which causes coronavirus disease 2019 (COVID-19), there is need for routine vaccination for both COVID-19 and influenza to reduce disease severity. Here, we prepared individual WPVs composed of formalin-inactivated SARS-CoV-2 WK 521 (Ancestral strain; Co WPV) or influenza virus [A/California/07/2009 (X-179A) (H1N1) pdm; Flu WPV] to produce a two-in-one Co/Flu WPV. Serum analysis from vaccinated mice revealed that a single dose of Co/Flu WPV induced antigen-specific neutralizing antibodies against both viruses, similar to those induced by either type of WPV alone. Following infection with either virus, mice vaccinated with Co/Flu WPV showed no weight loss, reduced pneumonia and viral titers in the lung, and lower gene expression of proinflammatory cytokines, as observed with individual WPV-vaccinated. Furthermore, a pentavalent vaccine (Co/qFlu WPV) comprising of Co WPV and quadrivalent influenza vaccine (qFlu WPV) was immunogenic and protected animals from severe COVID-19. These results suggest that a single dose of the two-in-one WPV provides efficient protection against SARS-CoV-2 and influenza virus infections with no evidence of vaccine interference in mice. We propose that concomitant vaccination with the two-in-one WPV can be useful for controlling both diseases.

Farm biosecurity practices affecting avian influenza virus circulation in commercial chicken farms in Bangladesh.

Avian influenza virus (AIV) is of major concern to livestock, wildlife, and human health. In many countries in the world, including Bangladesh, AIV is endemic in poultry, requiring improving biosecurity. In Bangladesh, we investigated how variation in biosecurity practices in commercial chicken farms affected their AIV infection status to help guide AIV mitigation strategies. We collected pooled fecal swabs from 225 farms and tested the samples for the AIV matrix gene followed by H5, H7, and H9 subtyping using rRT-PCR. We found that 39.6% of chicken farms were AIV positive, with 13% and 14% being positive for subtypes H5 and H9, respectively. Using a generalized linear mixed effects model, we identified as many as 12 significant AIV risk factors. Two major factors promoting AIV risk that cannot be easily addressed in the short term were farm size and the proximity of the farm to a live bird market. However, the other ten significant determinants of AIV risk can be more readily addressed, of which the most important ones were limiting access by visitors (reducing predicted AIV risk from 42 to 6%), isolation and treatment of sick birds (42 to 7%), prohibiting access of vehicles to poultry sheds (38 to 8%), improving hand hygiene (from 42 to 9%), not sharing farm workers across farms (37 to 8%), and limiting access by wild birds to poultry sheds (37 to 8%). Our findings can be applied to developing practical and cost-effective measures that significantly decrease the prevalence of AIV in chicken farms. Notably, in settings with limited resources, such as Bangladesh, these measures can help governments strengthen biosecurity practices in their poultry industry to limit and possibly prevent the spread of AIV.

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.

Comparison of factors associated with seasonal influenza and COVID-19 booster vaccination coverage among healthcare personnel working at acute care hospitals during 2021–2022 influenza season, National Healthcare Safety Network, United States

The simultaneous circulation of seasonal influenza virus and SARS-CoV-2 variants will likely pose unique challenges to public health during the future influenza seasons. Persons who are undergoing treatment in healthcare facilities may be particularly at risk. It is important for healthcare personnel to protect themselves and patients by receiving vaccines. The purpose of this study is to assess coverage of the seasonal influenza vaccine and COVID-19 monovalent booster among healthcare personnel working at acute care hospitals in the United States during the 2021–22 influenza season and to examine the demographic and facility characteristics associated with coverage. A total of 3260 acute care hospitals with over 7 million healthcare personnel reported vaccination data to National Healthcare Safety Network (NHSN) during the 2021–22 influenza season. Two separate negative binomial mixed models were developed to explore the factors associated with seasonal influenza coverage and COVID-19 monovalent booster coverage. At the end of the 2021–2022 influenza season, the overall pooled mean seasonal influenza coverage was 80.3%, and the pooled mean COVID-19 booster coverage was 39.5%. Several demographic and facility-level factors, such as employee type, facility ownership, and geographic region, were significantly associated with vaccination against influenza and COVID-19 among healthcare personnel working in acute care hospitals. Our findings highlight the need to increase the uptake of vaccination among healthcare personnel, particularly non-employees, those working in for-profit and non-medical school-affiliated facilities, and those residing in the South.

Study of features of influenza virus circulation in the southern region of Kazakhstan during the 2021 epidemic season

Influenza viruses are among the most prevalent infectious agents, leading to massive seasonal epidemics and pandemics with high mortality rates. The ability of influenza virus to antigenic variability determines the high population susceptibility, wide spread of infection, and short intervals between epidemics. In recent years, the co-circulation of influenza viruses that belong to A/H1N1pdm09 and A/ H3N2 subtypes and influenza type B virus has been observed. Here we summarize the data we explored to establish the features of the influenza virus circulation in the southern region of the Republic of Kazakhstan. To conduct virological and serological studies, 590 biosamples were collected from sick patients (419 swabs and 171 blood serums). Influenza type A virus RNA was found in 39 (9.31%) samples including that of A/H1N1pdm09 virus in 15 (3.58%), A/H3N2 virus in 23 (5.49%). It has also been noted that isolates A/Almaty/10/21 and A/Almaty/15/21 were profiled by the antigenic formula A/H3N2. The results of virological, serological, and molecular genetic studies confirm the simultaneous circulation of influenza A viruses (H1N1pdm09 and H3N2), and influenza type B virus. Some thoughts on the current scenario as well as implications for the future are presented as well.

Low Pathogenic Avian Influenza H9N2 Viruses in Morocco: Antigenic and Molecular Evolution from 2021 to 2023.

Avian influenza viruses pose significant threats to both the poultry industry and public health worldwide. Among them, the H9N2 subtype has gained substantial attention due to its high prevalence, especially in Asia, the Middle East, and Africa; its ability to reassort with other influenza viruses; and its potential to infect humans. This study presents a comprehensive phylogenetic and molecular analysis of H9N2 avian influenza viruses circulating in Morocco from 2021 to 2023. Through an active epidemiological survey, a total of 1140 samples (trachea and lungs) and oropharyngeal swabs pooled into 283 pools, collected from 205 farms located in 7 regions of Morocco known for having a high density of poultry farms, were analyzed. Various poultry farms were investigated (159 broiler farms, 24 layer farms, 10 breeder farms, and 12 turkey breeder farms). A total of 21 AI H9N2 strains were isolated, and in order to understand the molecular evolution of the H9N2 avian influenza virus, their genetic sequences were determined using the Sanger sequencing technique. Phylogenetic analysis was performed using a dataset comprising global H9N2 sequences to determine the genetic relatedness and evolutionary dynamics of the Moroccan strains. The results revealed the continued circulation and diversification of H9N2 avian influenza viruses in Morocco during the study period. Real-time RT-PCR showed a positivity rate of 35.6% (73/205), with cycle threshold values ranging from 19.2 to 34.9. The phylogenetic analysis indicated that all Moroccan strains belonged to a G1-like lineage and regrouped into two distinct clusters. Our newly detected isolates aggregated distinctly from the genotypes previously isolated in Morocco, North and West Africa, and the Middle East. This indicats the potential of virus evolution resulting from both national circulation and cross-border transmission. A high genetic diversity at both nucleotide and amino-acid levels was observed among all the strains isolated in this study, as compared to H9N2 strains isolated in Morocco since 2016, which suggests the co-circulation of genetically diverse H9N2 variants. Newly discovered mutations were detected in hemagglutinin positions 226, 227, and 193 (H3 numbering), which highlights the genetic evolution of the H9N2 AIVs. These findings contribute to our understanding of the evolution and epidemiology of H9N2 in the region and provide valuable insights for the development of effective prevention and control strategies against this emerging avian influenza subtype.