Objectives: The SARS-CoV-2 pandemic caused major morbidity, mortality, and economic disruption, highlighting the need to better understand zoonotic spillover risks posed by coronaviruses. We investigated whether archived human sera from forested Guinea contained evidence of prior exposure to coronaviruses antigenically related to known pathogenic human coronaviruses. Methods: Archived sera collected in 2017-2018 from wildlife hunter communities in Guinea were analysed using serological assays against spike glycoproteins from SARS-CoV, SARS-CoV-2, MERS-CoV, and seasonal human coronaviruses. Binding responses to receptor binding domains were also assessed, together with spatial and subgroup analyses. Results: Pre-pandemic sera showed IgG cross-reactivity to SARS-CoV, SARS-CoV-2, and MERS-CoV spike antigens. A distinct subgroup demonstrated strong binding to both SARS-CoV and MERS-CoV receptor binding domains. Conclusions: These findings highlight the utility of sero-epidemiology in identifying potential zoonotic spillover. However, further investigation is needed to identify these viruses and determine their homology to known pathogenic coronaviruses.

Respiratory syncytial virus (RSV) remains a leading cause of lower respiratory tract infection (LRTI) and hospitalization in early infancy. Following the introduction of universal nirsevimab prophylaxis in Italy during the 2024-2025 RSV season, we evaluated its real-world effectiveness against RSV-associated hospitalization and severe clinical outcomes within a test-negative design framework. We conducted a multicenter retrospective test-negative study across 88 Italian neonatal centers, including infants hospitalized for LRTI from 1 September 2024 to 30 April 2025. Clinical data were collected from hospital records using a standardized electronic questionnaire. RSV-positive hospitalized infants were considered cases, and RSV-negative hospitalized infants served as controls. Secondary outcomes included respiratory support and Neonatal Intensive Care Unit (NICU) admission. Effectiveness was estimated using multivariable logistic regression and targeted maximum likelihood estimation. Overall, 737 infants were included, of whom 306 (41.52%) had previously received nirsevimab. RSV infection was identified in 398 infants (54.00%), including 104/306 (33.99%) nirsevimab-immunized and 294/431 (68.21%) non-immunized infants (p < 0.001). Immunized infants also required respiratory support less frequently (55.23% vs. 70.07%; p < 0.001), with lower use of high-flow oxygen therapy (40.85% vs. 48.96%; p = 0.036) and Continuous Positive Airway Pressure (CPAP) (18.95% vs. 33.87%; p < 0.001). Within the test-negative design framework, adjusted effectiveness against RSV-associated hospitalization was estimated at 78.3%. Among hospitalized infants, previous nirsevimab immunization was additionally associated with adjusted relative reductions in the odds of respiratory support and NICU admission of 80.2% and 64.3%, respectively. In conclusion, among infants hospitalized for LRTI in routine Italian clinical practice, previous nirsevimab immunization was associated with lower odds of RSV positivity and a reduced need for respiratory support. Although these findings provide further evidence of the real-world effectiveness of nirsevimab against severe RSV disease, further studies are needed to provide direct estimates of hospitalization incidence in immunized and non-immunized source populations.

The H9N2 avian influenza virus (AIV) is currently widespread globally and poses a serious threat to the poultry industry and public health; however, its global epidemiological characteristics and key molecular mutation patterns have not yet been systematically elucidated. Based on the NCBI Influenza Virus Resource Database, this study collected relevant data on the H9N2 AIV from around the world between 1966 and 2023. It conducted a comprehensive analysis of the geographic distribution of 11,933 strains, the temporal distribution of 11,824 strains, the host sources of 11,756 strains, and the genetic polymorphisms at key functional sites. The results showed that 90.14% of H9N2 AIV sequences in the dataset originated from Asia, with China contributing the largest number of sequences. The global sequence availability pattern underwent four phases: sporadic sequence availability, gradual increase, high sequence availability, and subsequent decline, with 2007-2018 representing a period of relatively high availability of publicly accessible sequences. Host analysis indicated that H9N2 AIV sequences were predominantly derived from poultry-related hosts, with chickens being the main host source in the dataset, and available sequences have also been reported from various mammals, including pigs and humans, as well as environmental media. Molecular analysis revealed that receptor-binding-related sites in the HA protein, such as Q226L and I155T, have become dominant variants, while mammalian-adaptive mutations such as PB2 E627K and D701N remain at low frequencies; M2 S31N is widely prevalent, whereas the detection rate of NA drug-resistance-associated mutations is low. This study systematically reveals the global distribution patterns of available H9N2 AIV sequences, host distribution characteristics, and key molecular mutation patterns of the H9N2 AIV, providing a scientific basis for cross-host transmission risk assessment, molecular surveillance, and targeted prevention and control.

Severe COVID-19 is characterized by immune dysregulation, yet reliable biomarkers associated with adverse outcomes remain limited. Immunoglobulin G (IgG) N-glycosylation modulates antibody effector function and reflects the immune system's inflammatory state. In this study, we investigated whether specific IgG glycosylation profiles are associated with COVID-19 severity, mortality, and clinical course in patients without known prior SARS-CoV-2 infection. Of the 806 admitted COVID-19 patients included in the study, 377 hospitalized patients were longitudinally monitored, and 2001 serum samples were analyzed. Significant alterations in IgG N-glycome composition were observed in patients with severe disease and those who died. The most prominent changes included increased agalactosylation and decreased mono- and digalactosylation, features associated with a more pro-inflammatory IgG glycosylation profile. Nosocomial infections were associated with a more pro-inflammatory IgG glycosylation profile. No statistically significant differences in IgG N-glycome composition were observed between vaccinated and unvaccinated patients, although the small number of vaccinated patients limited this analysis. The observed glycomic profiles likely reflect immune responses characteristic of the early phase of the COVID-19 pandemic. Whether similar glycosylation changes occur in other infectious or inflammatory diseases remains to be established. IgG glycosylation analysis holds promise for personalized risk stratification and early therapeutic intervention in COVID-19 and other severe infectious diseases.

COVID-19 disease severity in unvaccinated individuals spans a striking continuum from complete absence of symptoms to life-threatening critical illness, yet the immunological determinants driving this divergence remain poorly understood. While Natural Killer (NK) cells and CD4⁺/CD8⁺ T cells mount distinct responses against SARS-CoV-2, the phenotypic and functional signatures distinguishing protective immunity from pathogenic immune dysfunction have yet to be defined. In the present study, we present a comparative analysis of NK cell and SARS-CoV-2-specific T cell immunity in unvaccinated symptomatic (SYMP) versus asymptomatic (ASYMP) COVID-19 patients. Using multicolor flow cytometry, we interrogated key immune checkpoints, the senescence marker CD57, differentiation status (CD45RA/CCR7), exhaustion marker PD-1, and activation markers HLA-DR and CD38, across NK and T cell subsets from SYMP patients, ASYMP patients, and Healthy Donors (HD). SYMP COVID-19 patients harbor significantly elevated co-expression of exhaustion and senescence markers on both NK and T cells relative to ASYMP patients and HD controls. Within the T cell compartment, SYMP patients exhibit broad dysregulation across naïve, central memory, effector memory, and terminally differentiated effector memory subsets, with CD57 enriched most prominently on CD8⁺ T_EM and CD8⁺ T_EMRA populations. While cytokine profiles did not significantly differ between ASYMP and SYMP patients, both groups showed markedly elevated pro-inflammatory TNF-α, IFN-γ, IL-6, IL-8, and IL-17 compared to HD controls, underscoring systemic immune activation as a hallmark of SARS-CoV-2 infection regardless of clinical severity. Taken together, these findings suggest that NK and T cell exhaustion and senescence are correlates of severe COVID-19, highlighting potential targets for future mechanistic and therapeutic investigation.

Cystic fibrosis (CF) is a rare, life-limiting genetic disorder characterized by abnormally thick mucus secretions that obstruct the respiratory, gastrointestinal, and reproductive tracts. Globally, CF affects an estimated 70,000 to 100,000 individuals. This study investigated nutritional awareness and dietary management among caregivers of pediatric CF patients. Specifically, it evaluated parental nutritional knowledge, caregiving behaviors, and patients' actual nutrient intake and diet quality relative to established clinical guidelines.

A cross-sectional study was conducted with a representative sample of 50 parents and their children with CF (aged 4-18 years) receiving specialized care at Caritas Baby Hospital in Bethlehem, Palestine. Data collection utilized a comprehensive parental questionnaire alongside a 3-day food diary completed by participants. Objective clinical status and biochemical markers were extracted directly from patients' medical records. CF-specific recommendations were used where available, and general pediatric reference values were used otherwise.

A significant disparity (p ≤ 0.05) was observed between patients' actual dietary intake and the recommended daily allowances for protein, carbohydrates, zinc, and calcium; however, intakes of sodium and iron did not differ significantly from guidelines. Higher patient adherence to dietary recommendations was significantly associated with superior lung function (measured via FEV1) and optimal serum albumin levels (p ≤ 0.05). Notably, 38% of the study sample were classified as underweight, and 76.9% of children with available 25(OH)D measurements (30/39) exhibited concentrations below 30 ng/mL. Clinical and biochemical measurements were not available for all participants. Caregiver nutritional knowledge was not significantly associated with the measured clinical or biochemical outcomes, whereas better patient dietary adherence was associated with higher FEV1% predicted and serum albumin concentrations.

The high prevalence of underweight status and micronutrient deficiencies highlights a critical need for targeted nutritional education and clinical counseling programs. Enhancing awareness among patients and parents is essential to correct dietary deficits, optimize growth, and improve long-term health outcomes.

The laboratory diagnosis of Legionnaires' disease (LD) remains a significant challenge due to the limitations of current methods. Most LD cases are diagnosed through the detection of Legionella urine antigen using commercial assays that are usually specific just for Legionella pneumophila (Lp) serogroup 1. Isolating Lp through culture is rarely done and difficult to achieve, especially due to two important issues: the low sensitivity of the method and the fact that it is difficult to obtain respiratory secretions from a significant proportion of patients. Real-time PCR (qPCR) has significantly improved LD diagnosis, indicating that molecular methods based on Legionella DNA detection can be highly effective. This study aimed to adapt a qPCR assay to a digital PCR (dPCR) assay, taking advantage of the more sensitive and more sophisticated dPCR technology. In particular, the study focused on 42 respiratory specimens, including bronchoalveolar lavage, tracheal aspirates, and sputum samples, with a particular focus on culture-negative specimens presumed to contain low concentrations of Legionella DNA, which were considered particularly suitable for assessing the potential of dPCR to improve the diagnosis of Legionnaires' disease. The results of culture, qPCR, and dPCR of respiratory samples were compared with each other and with data from urinary antigen tests (UATs) available for the corresponding patients. Overall, dPCR detected Legionella DNA in additional respiratory specimens compared with qPCR, corresponding to a 19% increase in the number of qPCR-negative specimens yielding a positive dPCR result. dPCR also detected Legionella DNA in specimens from patients with negative urinary antigen results. These findings suggest that dPCR may have potential as a complementary molecular approach for improving Legionella DNA detection in respiratory specimens, particularly in culture-negative samples. However, the clinical significance of dPCR-positive/qPCR-negative results could not be independently confirmed in this study and requires further investigation.

Respiratory tract infections (RTIs) caused by viruses are a public health problem, contributing to hospital admissions and morbidity worldwide. The COVID-19 pandemic substantially altered the detection patterns of respiratory viruses through public health interventions. Longitudinal data on these changes and viral seasonality remain limited in Saudi Arabia. This eight-year study evaluated epidemiological and seasonal patterns of major respiratory viruses across the COVID-19 era at a major Saudi tertiary care center.

A retrospective observational study was conducted at King Khalid University Hospital, Riyadh, from October 2017 to December 2025. PCR-confirmed detections for SARS-CoV-2, Influenza A, Influenza B, respiratory syncytial virus (RSV), and human metapneumovirus (HMPV) were extracted from the hospital Laboratory Information System. Demographics, co-detection, seasonality, and length of stay (LOS) were analyzed across four eras spanning the pre-COVID-19, lockdown, restriction, and post-restriction periods using descriptive statistics, the Kruskal-Wallis test, and multivariable negative binomial regression.

Among 5708 confirmed respiratory viral detection episodes, SARS-CoV-2 was the most frequently detected (52.5%), followed by Influenza A (19.1%), RSV (16.4%), Influenza B (8.4%), and HMPV (3.6%). Before the pandemic, Influenza A accounted for the largest proportion of detected episodes (71.1%), with detections clustering particularly during autumn and winter seasons, whereas SARS-CoV-2 accounted for the majority of detected episodes during the lockdown and restriction eras (97.4% and 93.2%). The post-restriction era became more diverse, with RSV being detected in substantial proportions (28.3%), showing prominent winter activity. RSV and HMPV predominantly affected children aged 0-5 years, whereas SARS-CoV-2 was more frequently detected among older adults. Among adults, older age was associated with prolonged LOS; Influenza A and HMPV were associated with shorter stays compared to SARS-CoV-2. Among children, no virus was independently associated with LOS after adjustment for age and sex; however, older age was associated with longer hospital stays.

The observed detection patterns of major respiratory viruses shifted substantially across the COVID-19 eras, with notable post-restriction diversification among observed positive detections. LOS was associated with age in both adults and children and with virus type among adults, supporting continued surveillance to guide preventive and clinical strategies.

Human respiratory viruses represent a major global health burden, causing millions of severe infections and deaths annually. Despite the central role of vaccines in prevention, their limitations, such as incomplete coverage, waning immunity, and vulnerability to viral evolution, underscore the urgent need for effective antiviral therapeutics. This review examines the principles and applications of target-based antiviral drug development against human respiratory viruses, emphasizing the identification and exploitation of conserved viral and host targets. Key viral proteins, including RNA-dependent RNA polymerases, proteases, and fusion glycoproteins, are analyzed across major virus families such as coronaviruses, paramyxoviruses, and adenoviruses, highlighting their structural features, functional constraints, and therapeutic potential. We further explore the integration of high-throughput screening and rational drug design, supported by advances in structural biology, cryo-electron microscopy, and computational approaches, including artificial intelligence-driven drug discovery. These methodologies collectively enhance the precision and efficiency of antiviral development. However, significant challenges remain, particularly the conflict between viral mutation and target conservation, the rapid emergence of drug resistance, and the safety limitations of host-targeted therapies. Finally, we discuss emerging strategies to overcome these barriers, including combination therapies and the development of broad-spectrum antivirals targeting conserved molecular mechanisms. This paper highlights a framework for the rational design of durable antiviral interventions capable of addressing both existing and emerging respiratory viral threats.

Viral infections are a widely recognized cause of mortality. Recently it has been demonstrated that vitamin D plays an important immuno-modulatory role in both innate and adaptive immune responses against infections, by reducing excessive inflammation and enhancing defense mechanisms. Specifically, exacerbation of infections may cause sepsis, characterized by a dysregulated immune response with hyperinflammation and immune exhaustion. Vitamin D can modulate these processes through various mechanisms, such as enhancing antiviral protection, promoting anti-inflammatory responses, protecting endothelial barriers, and modulating T-cells. This has been demonstrated for various viral infections, including influenza viruses, respiratory syncytial virus, and severe acute respiratory syndrome coronavirus. Although vitamin D deficiency has been associated with increased susceptibility to viral infections and immune cells of infected patients are highly responsive to vitamin D, the clinical benefits of its supplementation to vitamin D-deficient infected individuals are uncertain and, most importantly, direct evidence linking vitamin D to viral sepsis specifically remains particularly limited, with most mechanistic inference extrapolated from non-septic viral infection and bacterial sepsis literature. Based on these assumptions, this review will outline the present understanding about vitamin D regulatory effects on immune system and the possible connection between its serum levels and viral infections, while also addressing controversial issues.