Influenza B infections in children: A review

Influenza virus: Genomic insights, evolution, and its clinical presentation

Influenza viruses belong to the family Orthomyxoviridae and have been a concern for public health due to frequent epidemics and sporadic waves of pandemics. According to WHO, seasonal strains of the influenza A virus (IAV) infect 3 to 5 million people every year and result in 0.29-0.65 million deaths globally. Among all proteins of IAV, the hemagglutinin (HA) and neuraminidase (NA) have high mutation rates and have been reported to undergo antigenic drift and shift leading to novel strains. Hence continuous revision in drugs and vaccines regime is an economic burden as these reassortments can cause high morbidity among the immunologically naive population. Infection rates are higher among older age groups, infants and patients reported with other respiratory distress. Routine diagnostic tests include reverse transcription polymerase chain reaction (RT-PCR), viral culture, and immunofluorescence assays; however, the diagnosis may be hindered due to the resemblance of the clinical presentation of other respiratory viruses with influenza viruses. Here we present a comprehensive review which sheds light on the genomic structure, evolution, pathogenicity and clinical presentation of influenza virus that can help to distinguish it from other respiratory viruses. A detailed analysis will ultimately pave the way for the development of more effective antiviral drugs and a universal vaccine.

Life-Threatening Anemia and Thrombocytopenia in a Toddler with Influenza B: Case Report and Literature Review

Background: Seasonal influenza viruses are primarily known for causing respiratory illness, but rare hematologic complications can occur, especially in young children. While influenza A is more commonly linked to severe manifestations, influenza B can similarly precipitate life-threatening cytopenias, particularly in toddlers. Case Presentation: We report the case of a previously healthy 1-year-and-8-months-old girl who presented with a high fever, cough, and marked pallor during peak influenza season. Laboratory tests revealed significant microcytic, hypochromic anemia and severe thrombocytopenia. Rapid antigen testing was positive for influenza B. An extensive workup for other causes of bicytopenia, including leukemia, hemolysis, aplastic anemia, and other viral infections, yielded negative results. The child was managed with urgent red blood cell and platelet transfusions, oseltamivir antiviral therapy, broad-spectrum antibiotics, corticosteroids, and supportive care. Bone marrow aspiration was deferred in light of the rapid hematologic recovery. Her hemoglobin greatly improved, and her platelet count reached normal values at discharge. Conclusions: Our case underscores the need to consider influenza in the differential diagnosis of unexplained cytopenias during flu season. This case illustrates that influenza B can mimic hematologic malignancies. Rapid diagnosis and supportive treatment are essential to avoid fatal outcomes. Influenza vaccination plays a significant role in preventing severe complications, such as those we encountered.

Comparison of Efficacy and Safety of Baloxavir and Oseltamivir in Children With Influenza: A Systematic Review and Meta-Analysis

This systematic review and meta-analysis compared the efficacy and safety of baloxavir marboxil and oseltamivir in treating influenza in children. A comprehensive literature search was conducted across multiple databases, identifying five studies (four observational and one randomized controlled trial) with a pooled sample size of 2,261 patients. The analysis revealed that baloxavir marboxil significantly reduced the duration of fever compared to oseltamivir (mean difference: -13.49 hours, 95% CI: -23.75 to -3.24). However, there was no significant difference in the time to resolution of overall influenza symptoms between the two treatments (mean difference: -4.55 hours, 95% CI: -19.48 to 10.37). Safety analysis, though limited by available data, suggested a lower incidence of nausea and vomiting with baloxavir marboxil compared to oseltamivir. Both drugs demonstrated comparable safety profiles for other adverse events. These findings indicate that while both medications remain viable options for managing pediatric influenza, baloxavir marboxil may offer advantages in terms of rapid fever reduction and potentially fewer gastrointestinal side effects. However, the study highlights the need for more robust, large-scale randomized controlled trials focusing exclusively on pediatric populations to strengthen the evidence base. Clinicians should consider individual patient factors, local resistance patterns, and current guidelines when making treatment decisions. Future research should explore combination therapies and their potential to manage severe influenza cases in children and conduct more comprehensive safety assessments in pediatric populations.

Different effects of air pollutant concentrations on influenza A and B in Sichuan, China

BACKGROUND

The detrimental effects of air pollution on the respiratory system are well documented. Previous research has established a correlation between air pollutant concentration and the frequency of outpatient visits for influenza-like illness. However, studies investigating the variations in infection among different influenza subtypes remain sparse. We aimed to determine the correlation between air pollutant levels and different influenza subtypes in Sichuan Province, China.

METHODS

A generalized additive model and distributed lag nonlinear model were employed to assess the association between air pollutants and influenza subtypes, utilizing daily influenza data obtained from 30 hospitals across 21 cities in Sichuan Province. The analysis considered the temporal effects and meteorological factors. The study spanned from January 1, 2017, to December 31, 2019. To provide a more precise evaluation of the actual impact of air pollution on different subtypes of influenza, we also performed subgroup analyses based on factors such as gender, age, and geography within the population.

RESULTS

During the investigation, 17,462 specimens from Sichuan Province tested positive for influenza. Among these, 12,607 and 4855 were diagnosed with Flu A and B, respectively. The related risk of influenza A infection significantly increased following exposure to PM2.5 on Lag2 days (RR=1.008, 95 % confidence interval [CI]: 1.000-1.016), SO2 and CO on Lag1 days (RR=1.121, 95 % CI: 1.032-1.219; RR=1.151, 95 % CI: 1.030-1.289), and NO2 on Lag0 day (RR=1.089, 95 % CI: 1.035-1.145). PM10 and SO2 levels on Lag0 day, PM2.5 levels on Lag1 day, and CO levels on Lag6 day, with a reduced risk of influenza B (RR=0.987, 95 % CI: 0.976-0.997; RR=0.817, 95 % CI: 0.676-0.987; RR=0.979, 95 % CI: 0.970-0.989; RR=0.814, 95 % CI: 0.561-0.921).

CONCLUSION

The findings from the overall population and subgroup analyses indicated that the impact of air pollutant concentrations on influenza A and B is inconsistent, with influenza A demonstrating greater susceptibility to these pollutants. Minimizing the levels of SO2, CO, NO2, and PM2.5 can significantly decrease the likelihood of contracting influenza A. Analyzing the influence of environmental contaminants on different influenza subtypes can provide insights into seasonal influenza trends and guide the development of preventive and control strategies.

Co-circulation of seasonal influenza A(H1N1)pdm09, A(H3N2) and B/Victoria lineage viruses with further genetic diversification, EU/EEA, 2022/23 influenza season

BackgroundInfluenza viruses can cause large seasonal epidemics with high healthcare impact and severity as they continually change their virological properties such as genetic makeup over time.AimWe aimed to monitor the characteristics of circulating influenza viruses over the 2022/23 influenza season in the EU/EEA countries. In addition, we wanted to compare how closely the circulating viruses resemble the viral components selected for seasonal influenza vaccines, and whether the circulating viruses had acquired resistance to commonly used antiviral drugs.MethodsWe performed a descriptive analysis of the influenza virus detections and characterisations reported by National Influenza Centres (NIC) from the 30 EU/EEA countries from week 40/2022 to week 39/2023 to The European Surveillance System (TESSy) as part of the Global Influenza Surveillance and Response System (GISRS).ResultsIn the EU/EEA countries, the 2022/23 influenza season was characterised by co-circulation of A(H1N1)pdm09, A(H3N2) and B/Victoria-lineage viruses. The genetic evolution of these viruses continued and clade 6B.1A.5a.2a of A(H1N1)pdm09, 3C.2a1b.2a.2b of A(H3N2) and V1A.3a.2 of B/Victoria viruses dominated. Influenza B/Yamagata-lineage viruses were not reported.DiscussionThe World Health Organization (WHO) vaccine composition recommendation for the northern hemisphere 2023/24 season reflects the European virus evolution, with a change of the A(H1N1)pdm09 component, while keeping the A(H3N2) and B/Victoria-lineage components unchanged.

Influenza B Virus Receptor Specificity: Closing the Gap between Binding and Tropism

Influenza A and influenza B viruses (FLUAV and FLUBV, respectively) cause significant respiratory disease, hospitalization, and mortality each year. Despite causing at least 25% of the annual disease burden, FLUBV is historically understudied. Unlike FLUAVs, which possess pandemic potential due to their many subtypes and broad host range, FLUBVs are thought to be restricted to only humans and are limited to two lineages. The hemagglutinins (HA) of both influenza types bind glycans terminating in α2,6- or α2,3-sialic acids. For FLUAV, the tropism of human- and avian-origin viruses is well-defined and determined by the terminal sialic acid configuration the HA can accommodate, with avian-origin viruses binding α2,3-linked sialic acids and human-origin viruses binding α2,6-linked sialic acids. In contrast, less is known about FLUBV receptor binding and its impact on host tropism. This review discusses the current literature on FLUBV receptor specificity, HA glycosylation, and their roles in virus tropism, evolution, and infection. While the focus is on findings in the past dozen years, it should be noted that the most current approaches for measuring virus-glycan interactions have not yet been applied to FLUBV and knowledge gaps remain.

Impact of Pre-Existing Immunity and Age on Antibody Responses to Live Attenuated Influenza Vaccine

Live attenuated influenza vaccines (LAIV) typically induce a poor hemagglutination inhibition (HI) response, which is the standard correlate of protection for inactivated influenza vaccines. The significance of the HI response is complicated because the LAIV vaccine primarily induces the local mucosal immune system, while the HI assay measures the circulating serum antibody response. However, age and pre-existing immunity have been identified as important factors affecting LAIV immunogenicity. This study aimed to extend our understanding of LAIV-induced immunity, particularly, the impact age and pre-existing immunity have on eliciting functional and neutralising antibody responses in paediatric and adult populations vaccinated with LAIV. Thirty-one children and 26 adults were immunized with the trivalent LAIV during the 2013-2014 influenza season in Norway. Children under 9 years received a second dose of LAIV 28 days after the first dose. Blood samples were collected pre- and post-vaccination. HI, microneutralization (MN) and enzyme-linked lectin assay for neuraminidase (NA) antibodies were measured against the vaccine strains. IgG antibody avidity against hemagglutinin (HA) and NA proteins from the vaccine strains was also assessed. Significant correlations were observed between HI and MN responses to A/California/7/2009 (A/H1N1)pdm09-like strain and B/Massachusetts/2/2012-like strain, suggesting that MN is a potential immunological correlate for LAIV. However, the relationship between recipient age (or priming status) and serological response varied between vaccine strains. There was a notable increase in HI and MN responses in all cohorts except naive children against the H1N1 strain, where most recipients had responses below the protective antibody threshold. NAI responses were generally weak in naive children against all vaccine strains compared with adults or antigen-primed children. Post-vaccination antibody avidity increased only in primed children below nine years of age against the A/H1N1 strain. Overall, our findings indicate that LAIV elicits functional and neutralizing antibody responses in both naive and antigen experienced cohorts, however, the magnitude and kinetics of the response varies between vaccine strains.

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.

Severe acute respiratory infections: An epidemiological analysis of surveillance data in Bahrain, 2018-2022

Background

Severe acute respiratory tract infections (SARI) pose a health threat to children and adults worldwide. The SARI surveillance program was initiated in 2018 in Bahrain to monitor the activity of respiratory pathogens. Salmaniya Medical Complex (SMC) was chosen as the sentinel site for the SARI surveillance program. This study aimed to describe the epidemiology of SARI patients admitted to SMC from 2018 to 2022.

Methods

Patients meeting the World Health Organization definition of SARI and presenting with cough and fever within the last 10 days and admitted to SMC from January 2018 until December 2022 were included in the study. Epidemiological data on SARI cases were collected from SARI surveillance data and analyzed using SPSS version 25 and Excel.

Results

A total of 1362 SARI cases were enrolled from January 2018 to the end of December 2022; the majority were males (57.7%, n = 786). The highest SARI incidence rates were recorded among individuals over 65 years old (155.5 per 100,000) in 2021 and among those under 5 years old (887 per 100,000) in 2020. About half of the patients had at least one comorbidity (54.0%, n = 735), with diabetes (23.0%, n = 313) and hypertension (17.2%, n = 234) being the most common. The highest number of cases was observed in 2021 (27%, n = 373), followed by 2018 (20%, n = 267). A viral pathogen was detected in 30.7% (n = 418) of the SARI patients. The most prevalent pathogen was influenza A (11.5%, n = 156), followed by SARS-CoV-2 (9.7%, n = 132), respiratory syncytial virus (RSV) (5.1%, n = 69), and influenza B (3.9%, n = 53). The highest percentage of SARI cases was recorded in the winter months, mainly January (17%, n = 236). The percentages of influenza A and RSV cases were highest in December, at 22% (n = 39) and 14% (n = 25), respectively. Influenza B cases were recorded predominantly in March (9%, n = 11).

Conclusion

The incidence of SARI was highest among patients above 65 years old. The majority had comorbidities. Influenza and respiratory syncytial viruses were the most frequent causes of SARI, with influenza A being the most prevalent. December and January were the months with the highest SARI cases and viral detection rates. Promoting vaccination, timely testing, and prompt treatment, especially for the elderly and those with comorbidities, is key to reducing SARI-related morbidity and mortality, especially during peak seasons.

Performance evaluation of a SARS-CoV-2 and influenza A/B combo rapid antigen test

Introduction: The global COVID-19 pandemic and seasonal influenza outbreaks have drawn attention to the critical need for accurate and efficient diagnostic tools. Methods: The performance of the InstaView COVID-19/Flu Ag Combo Test, which was designed to simultaneously detect the SARS-CoV-2, influenza A, and influenza B viruses, was analytically and clinically evaluated. Results: The InstaView COVID-19/Flu Ag Combo Test exhibited robust detection capabilities, accurately identifying SARS-CoV-2, influenza A, and influenza B viruses over a wide concentration range (1.41 × 103 to 7.05 × 104 TCID50/mL). Extensive testing against potential cross-reactants and interferences yielded no false-positive results, indicating the high specificity of the test. Clinical evaluation further confirmed the kit's reliability, with sensitivity ranging from 95.1% to 98.2% for SARS-CoV-2, 88.9%-95.2% for influenza A, and 91.7%-100% for influenza B depending on the sample type. The specificity was consistently 100% for all of the targeted viruses. Discussion: The InstaView COVID-19/Flu Ag Combo Test thus demonstrated high performance, ease of use, rapid results, and the ability to precisely detect SARS-CoV-2 and influenza A/B infections, making it an effective tool in streamlining diagnostic workflows, optimizing resource allocation, and improving patient outcomes.

Clinical Features and Outcomes of the Association of Co-Infections in Children with Laboratory-Confirmed Influenza during the 2022-2023 Season: A Romanian Perspective

The 2022-2023 influenza season in Romania was characterized by high pediatric hospitalization rates, predominated due to influenza A subtypes (H1N1) pdm09 and H3N2. The lowered population immunity to influenza after the SARS-CoV-2 pandemic and the subsequent stoppage of influenza circulation, particularly in children who had limited pre-pandemic exposures, influenced hospitalization among immunosuppressed children and patients with concurrent medical conditions who are at an increased risk for developing severe forms of influenza. This study focused on the characteristics of influenza issues among pediatric patients, as well as the relationship between different influenza virus types/subtypes and viral and bacterial co-infections, as well as illness severity in the 2022-2023 season after the SARS-CoV-2 pandemic. We conducted a retrospective clinical analysis on 301 cases of influenza in pediatric inpatients (age ≤ 18 years) who were hospitalized at the National Institute of Infectious Diseases "Prof. Dr. Matei Balș" IX Pediatric Infectious Diseases Clinical Section between October 2022 and February 2023. The study group's median age was 4.7 years, and the 1-4 year age group had the highest representation (57.8%). Moderate clinical forms were found in 61.7% of cases, whereas severe versions represented 18.2% of cases. Most of the complications were respiratory (acute interstitial pneumonia, 76.1%), hematological (72.1%, represented by intra-infectious and deficiency anemia, leukopenia, and thrombocytopenia), and 33.6% were digestive, such as diarrheal disease, liver cytolysis syndrome, and the acute dehydration syndrome associated with an electrolyte imbalance (71.4%). Severe complications were associated with a risk of unfavorable evolution: acute respiratory failure and neurological complications (convulsions, encephalitis). No deaths were reported. We noticed that the flu season of 2022-2023 was characterized by the association of co-infections (viral, bacterial, fungal, and parasitic), which evolved more severely, with prolonged hospitalization and more complications (p < 0.05), and the time of use of oxygen therapy was statistically significant (p < 0.05); the number of influenza vaccinations in this group was zero. In conclusion, co-infections with respiratory viruses increase the disease severity of the pediatric population to influenza, especially among young children who are more vulnerable to developing a serious illness. We recommend that all people above the age of six months should receive vaccinations against influenza to prevent the illness and its severe complications.

Fc-Effector-Independent in vivo Activity of a Potent Influenza B Neuraminidase Broadly Neutralizing Antibody

Influenza B virus (IBV) contributes to substantial influenza-mediated morbidity and mortality, particularly among children. Similar to influenza A viruses (IAV), the hemagglutinin (HA) and neuraminidase (NA) of IBV undergo antigenic drift, necessitating regular reformulation of seasonal influenza vaccines. NA inhibitors, such as oseltamivir, have reduced activity and clinical efficacy against IBV, while M2 channel inhibitors are only effective against IAV, highlighting the need for improved vaccine and therapeutics for the treatment of seasonal IBV infections. We have previously described a potent human monoclonal antibody (hMAb), 1092D4, that is specific for IBV NA and neutralizes a broad range of IBVs. The anti-viral activity of MAbs can include direct mechanisms such as through neutralization and/or Fc-mediated effector functions that are dependent on accessory cells expressing Fc receptors and that could be impacted by potential host-dependent variability. To discern if the in vivo efficacy of 1092D4 was dependent on Fc-effector function, 1092D4 hMAb with reduced ability to bind to Fc receptors (1092D4-LALAPG) was generated and tested. 1092D4-LALAPG had comparable in vitro binding, neutralization, and inhibition of NA activity to 1092D4. 1092D4-LALAPG was effective at protecting against a lethal challenge of IBV in mice. These results suggest that hMAb 1092D4 in vivo activity is minimally dependent on Fc-effector functions, a characteristic that may extend to other hMAbs that have potent NA inhibition activity.

Early peripheral blood lymphocyte subsets and cytokines in predicting the severity of influenza B virus pneumonia in children

Background

Children with influenza B virus infection have a higher susceptibility and higher severity of illness. The activation and disorder of immune function play an important role in the severity of influenza virus infection. This study aims to investigate whether early lymphocyte count and cytokines can provide predictive value for the progression in children with influenza B virus pneumonia.

Methods

A retrospective cohort study was conducted to analyze the clinical data of children with influenza B virus pneumonia from December 1, 2021, to March 31, 2022, in the National Children's Regional Medical Center (Shengjing Hospital of China Medical University). According to the severity of the disease, the children were divided into a mild group and a severe group, and the clinical characteristics, routine laboratory examination, lymphocyte subsets, and cytokines were compared.

Results

A total of 93 children with influenza B virus pneumonia were enrolled, including 70 cases in the mild group and 23 cases in the severe group. Univariate analysis showed that drowsiness, dyspnea, white blood cell (WBC), lymphocytes, monocytes, procalcitonin, alanine aminotransferase (ALT), aspartate aminotransferase (AST), creatine kinase-MB (CK-MB), lactate dehydrogenase (LDH), fibrinogen (FIB), Immunoglobulin M (IgM), lung consolidation, total T cell count, CD4⁺ T cell count, CD8⁺ T cell count, NK cell count, NK cell % and B cell % had statistical differences between the mild and severe groups (P<0.05). In multivariate logistic regression analysis, reduced ALT (OR = 1.016), FIB (OR = 0.233), CD8⁺ T cell count (OR = 0.993) and NK cell count (OR = 0.987) were independently associated with the development of severe influenza B virus pneumonia.

Conclusions

The levels of T lymphocytes and NK cells were related to the progression of influenza B virus pneumonia in children, and the reduction of CD8⁺ T cell count and NK cell count can be used as independent risk factors for predicting the severity of influenza B virus pneumonia.

Development of an AlphaLISA assay for sensitive and accurate detection of influenza B virus

Objective

Influenza B virus (IBV) is highly contagious, spreads rapidly, and causes seasonal epidemic respiratory disease in the human population, especially in immunocompromised people and young children. Clinical manifestations in this high-risk population are often more severe than in immunocompetent hosts and sometimes atypical. Therefore, rapid, and accurate detection of IBV is important.

Methods

An amplified luminescent proximity homogeneous assay linked immunosorbent assay (AlphaLISA) was developed for detection of IBV by optimizing the ratio of IBV antibody-labeled receptor beads, streptavidin-conjugated donor beads and biotinylated IBV antibody, as well as the optimal temperature and time conditions for incubation. Assay sensitivity, specificity and reproducibility were evaluated. A total of 228 throat swab samples and inactivated influenza B virus were tested by AlphaLISA and lateral flow colloidal gold-based immunoassay (LFIA).

Results

AlphaLISA produced the best results for detection of inactivated influenza B virus when IBV antibody-labeled acceptor beads were 50 μg/ mL, streptavidin-conjugated donor beads were 40 μg/mL, and biotinylated IBV antibody was 0.5 μg/mL at 37°C for 15-10 min. Under these conditions, AlphaLISA had a limit of detection of 0.24 ng/mL for the detection of influenza B nucleoprotein, did not cross react with other common respiratory viruses, and showed good reproducibility with inter-assay coefficient of variation (CV) and intra-assay CV < 5%. The results of 228 clinical throat swab samples showed good agreement between AlphaLISA and LFIA (Kappa = 0.982), and AlphaLISA showed better sensitivity than LFIA for detecting inactivated influenza B virus.

Conclusion

AlphaLISA showed higher sensitivity and throughput in the detection of IBV and can be used for IBV diagnosis and epidemic control.

Modeling the effects of cigarette smoke extract on influenza B virus infections in mice

Influenza B virus (IBV) is a major respiratory viral pathogen. Due to a lack of pandemic potential for IBV, there is a lag in research on IBV pathology and immunological responses compared to IAV. Therefore, the impact of various lifestyle and environmental factors on IBV infections, such as cigarette smoking (CS), remains elusive. Despite the increased risk and severity of IAV infections with CS, limited information exists on the impact of CS on IBV infections due to the absence of suitable animal models. To this end, we developed an animal model system by pre-treating mice for two weeks with cigarette smoke extract (CSE), then infected them with IBV and monitored the resulting pathological, immunological, and virological effects. Our results reveal that the CSE treatment decreased IBV specific IgG levels yet did not change viral replication in the upper airway/the lung, and weight recovery post infection. However, higher concentrations of CSE did result in higher mortality post infection. Together, this suggests that CS induced inflammation coupled with IBV infection resulted in exacerbated disease outcome.

Differentiation of influenza B lineages circulating in different regions of Brazil, 2014 – 2016, using molecular assay

Background

Two antigenically and genetically distinct lineages of influenza B viruses (B/Victoria and B/Yamagata) have been co-circulating worldwide since 2002. Virological surveillance is essential to differentiate between both lineages with a view to the annual updating of the B component for the trivalent or quadrivalent influenza vaccine composition.

Methods

The samples analyzed in the present study were collected by influenza sentinel units located in the Southeast, Midwest, North, and Northeast regions of Brazil, part of the National Influenza Virus Surveillance Network, coordinated by the Ministry of Health of Brazil. A total of 870 influenza B positive samples by reverse transcription real – time polymerase chain reaction (RT-qPCR), collected during 2014, 2015, and 2016 influenza seasons, were submitted to the influenza B lineage genotyping panel for characterization as B/Yamagata or Victoria lineages using RT-qPCR.

Results

Of the 197 samples analyzed in 2014, a total of 160 (81 %) corresponded to the B/Yamagata lineage, 19 (10 %) to the B/Victoria lineage, and 18 (9 %) to indeterminate lineages. Of the 190 samples analyzed in 2015, a total of 124 (65 %) corresponded to the B/Yamagata lineage; 55 (29 %) to the B/Victoria lineage, whereas 11 (6 %) were of indeterminate lineages. Of the 483 samples analyzed in 2016, a total of 297 (62 %) corresponded to the B /Victoria lineage; 174 (36 %) to the B/Yamagata lineage and 12 (2 %) to indeterminate lineages. This cross-sectional study revealed influenza B virus (IBV) infection in all age groups, and among them, the highest prevalence was observed in individuals between 11 and 49 years of age Our findings demonstrate the match between influenza B virus lineages recommended by the World Health Organization (WHO) for the trivalent vaccine composition to be used in the Southern Hemisphere (SH) and the predominant circulating viruses during the 2014, 2015, and 2016 seasons.

Incidence and neutralizing antibody seroprevalence of influenza B virus in Egypt: Results of a community-based cohort study

Since 2000, two lineages of influenza B viruses, Victoria and Yamagata, have been circulating at similar frequencies worldwide. Little is known about the circulation of those viruses in Egypt. This study aims to describe the epidemiology of influenza B virus infections in Egypt, 2017–2019. This was performed through a household prospective cohort study on influenza infections among 2400 individuals from five villages. When a study participant had influenza like symptoms, a nasal swab and an oropharyngeal swab were obtained and tested by RT-PCR for influenza B infections. A serum sample was obtained from all participants annually to detect neutralizing antibodies using microneutralization assay. 9.1% of subjects were positive for influenza B viruses during season 2017–2018 mostly among preschoolers and 7.6% were positive during the season 2018–2019 with higher risk in females, potentially due to mothers being infected after contact with their children. The overall seroprevalence among the participants was 53.2% and 52.2% against the Victoria and Yamagata lineages respectively, the majority of seropositive participants were students. Multivariate analysis showed that age and having chronic diseases were the strongest predictors of infection. Our results show that both influenza B lineages circulated between 2017 and 2020 in Egypt almost in equal proportion. Encouraging the uptake of seasonal influenza vaccines is recommended.

Human SUMOylation Pathway Is Critical for Influenza B Virus

The identification and elucidation of host pathways for viral infection are critical for understanding the viral infection processes and novel therapeutics development. Here, for the first time, we discover that the human SUMOylation pathway is essential for the IBV viral life cycle. First, IBV viruses were completely inhibited by a novel SUMOylation specific inhibitor, STE025, discovered from our FRET-based high-throughput screening, and the inhibition was very potent, with IC50~ 0.1 µM in an IBV-induced cell death rescue assay; Second, we determined that the IBV M1 protein was SUMOylated, which was mediated by the SUMOylation E2 conjugation enzyme and the E3 ligase enzyme at very high affinities, of 0.20 µM and 0.22 µM, respectively; Third, the mutation of the IBV M1 SUMOylation site, K21R, completely abolished the viral particle generation, strongly suggesting the requirement of SUMOylation for the IBV life cycle. These results suggest that the blockage of the host human SUMOylation pathway is very effective for IBV inhibition. We therefore propose that the host SUMOylation pathway is a critical host factor for the IBV virus life cycle. The identification and inhibition of critical host factor(s) provide a novel strategy for future anti-viral therapeutics development, such as IBV and other viruses.