OBJECTIVES: To investigate the epidemiological characteristics of human metapneumovirus (hMPV) and the risk factors for severe pneumonia in hospitalized children. METHODS: The epidemiological characteristics of hMPV in hospitalized children at Hebei Children's Hospital from January 2019 to December 2023 were retrospectively analyzed. The clinical data of hospitalized children with hMPV infection from April to December 2023 were included, and independent risk factors for severe pneumonia were identified through logistic regression. RESULTS: A total of 44 092 children were tested, with an hMPV positive rate of 7.30% (3 220/44 092). Children aged 3-6 years constituted the largest proportion (40.93%, 1 318/3 220) among hMPV-positive cases. The detection rate varied significantly by year (P<0.001), peaking in 2022 (12.35%, 978/7 919). The peak season of the epidemic was winter and spring from 2019 to 2021, but shifted to spring and summer from 2022 to 2023. The proportion of co-infection was 38.70% (1 246/3 220), primarily with rhinovirus (600/1 246, 48.15%), Mycoplasma pneumoniae (217/1 246, 17.42%), and respiratory syncytial virus (182/1 246, 14.61%). The main manifestations of hMPV pneumonia were cough, expectoration, and fever. Children with severe pneumonia were significantly younger (P<0.05). Wheezing, underlying diseases, co-infection, and younger age were identified as independent risk factors for severe pneumonia (P<0.05). CONCLUSIONS There are significant annual and seasonal differences in the epidemiological characteristics of hMPV in hospitalized children. Young age, underlying diseases, wheezing, and co-infection are independent risk factors for severe pneumonia.
Humans ; Risk Factors ; Metapneumovirus ; Child, Preschool ; Child ; Male ; Female ; Paramyxoviridae Infections/complications* ; Pneumonia/epidemiology* ; Retrospective Studies ; Child, Hospitalized ; Infant ; Logistic Models ; Seasons ; Hospitalization

Paramyxoviruses are important respiratory pathogens with substantial clinical relevance in pediatric infectious diseases. During infection, multiple forms of programmed cell death (PCD) may be induced, and this plays pivotal roles in viral replication, dissemination, and host immune responses, thereby profoundly influencing the viral life cycle and disease progression. On one hand, PCD facilitates the clearance of infected cells, restricts viral spread, and activates host immune defenses, thereby enhancing antiviral immunity. On the other hand, excessive or dysregulated cell death may lead to tissue damage and immune imbalance, creating a microenvironment conducive to viral replication and exacerbating disease severity. For instance, apoptosis-mediated by both extrinsic and intrinsic pathways-contributes to infection control but may also be hijacked by viruses to promote dissemination. Pyroptosis, driven by inflammasome activation, triggers lytic cell death and the release of pro-inflammatory cytokines. Necroptosis, mediated by the RIPK1-RIPK3-MLKL signaling axis, and pyroptosis both amplify innate immune responses but may concurrently induce inflammatory dysregulation. Immunogenic cell death (ICD), characterized by the release of damage-associated molecular patterns and neoantigens, activates antigen-specific immune responses and holds therapeutic potential for antiviral and antitumor interventions. Emerging evidence suggests that ferroptosis, through the modulation of iron metabolism and associated transporters, may also participate in viral replication and infected cell clearance. This review comprehensively summarizes the roles of apoptosis, pyroptosis, necroptosis, ICD, and ferroptosis in paramyxovirus infection, aiming to deepen the understanding of paramyxovirus pathogenesis and to provide insights for developing novel antiviral strategies.
Humans ; Paramyxoviridae Infections/pathology* ; Pyroptosis ; Apoptosis ; Virus Replication ; Necroptosis ; Inflammasomes ; Immunity, Innate ; Immunogenic Cell Death ; Paramyxoviridae/physiology* ; Signal Transduction

Human parainfluenza viruses (HPIVs) is one of the main causes of acute respiratory tract infections in children. HPIVs have been grouped into four serotypes (HPIV1~HPIV4) according to serological and genetic variation. Different serotypes of HPIVs have diverse clinical disease spectrum, epidemic characteristics and disease burden. Based on the nucleotide variation in structural protein genes, HPIVs can be further divided into distinct genotypes and subtypes with diverse temporal and spatial distribution features. The standard molecular typing methods are helpful to clarify the gene evolution and transmission patterns of HPIVs in the process of population transmission. However, the development of molecular epidemiology of HPIVs has been hindered by the lack of a standardized molecular typing method worldwide. Therefore, this study reviewed the viral characteristics, genome structure, existing genotyping methods and evolution of HPIVs, and screened the reference strains for molecular typing, so as to improve the understanding of gene characteristics and molecular typing of HPIVs, and provide an important scientific basis for the monitoring and research of molecular epidemiology of HPIVs in China.
Child ; Humans ; Molecular Typing ; Parainfluenza Virus 1, Human/genetics* ; Parainfluenza Virus 2, Human/genetics* ; Parainfluenza Virus 3, Human/genetics* ; Paramyxoviridae Infections/epidemiology* ; Respiratory Tract Infections/epidemiology*

Viral respiratory infections are one of the most common infections worldwide. It is important to detect the virus early and precisely. In this study, we evaluated the limit of detection (LoD) and usefulness of the Real-Q RV Detection kit (BioSewoom, Seoul, Korea). We measured the LoD of the Real-Q RV Detection kit using 10 strains of standard viruses. We then compared the detection results by the Allplex Respiratory Panel Assay kit (Seegene, Seoul, Korea) using 123 clinical specimens. The discrepant results were confirmed by sequencing. Among the 10 standard viruses, the LoD of human rhinovirus (HRV) was the lowest and that of parainfluenza virus 2 and 3 was relatively high as detected by Real-Q RV Detection kit. Agreements of the two kits ranged from 95.9% to 100%. Three specimens detected negative by the Allplex Respiratory Panel kit were detected as adenovirus (AdV) by the Real-Q RV Detection kit and were confirmed by sequencing. Similarly, a specimen detected negative by the Allplex Respiratory Panel kit was detected as HRV by the Real-Q RV Detection kit and was confirmed by sequencing. A specimen detected as human enterovirus by the Allplex Respiratory Panel kit was detected as HRV by the Real-Q RV Detection kit and was confirmed by sequencing. Real-Q RV Detection kit showed good diagnostic performance and can be useful for detecting major viruses that cause respiratory infections.
Adenoviridae ; Enterovirus ; Humans ; Limit of Detection ; Paramyxoviridae Infections ; Respiratory Tract Infections* ; Rhinovirus ; Seoul

PURPOSE: The most common cause of acute exacerbation of chronic obstructive pulmonary disease (AECOPD) is respiratory infection. Most studies of bacterial or viral cause in AECOPD have been conducted in Western countries. We investigated bacterial and viral identification rates in AECOPD in Korea. MATERIALS AND METHODS: We reviewed and analyzed medical records of 736 cases of AECOPD at the Korea University Guro Hospital. We analyzed bacterial and viral identification rates and classified infections according to epidemiological factors, such as Global Initiative for Chronic Obstructive Lung Disease stage, mortality, and seasonal variation. RESULTS: The numbers of AECOPD events involving only bacterial identification, only viral identification, bacterial-viral co-identification, and no identification were 200 (27.2%), 159 (21.6%), 107 (14.5%), and 270 (36.7%), respectively. The most common infectious bacteria identified were Pseudomonas aeruginosa (13.0%), Streptococcus pneumoniae (11.4%), and Haemophilus influenzae (5.3%); the most common viruses identified were influenza virus (12.4%), rhinovirus (9.4%), parainfluenza virus (5.2%), and metapneumovirus (4.9%). The bacterial identification rate tended to be higher at more advanced stages of chronic obstructive pulmonary disease (p=0.020 overall, p=0.011 for P. aeruginosa, p=0.048 for S. pneumoniae). Staphylococcus aureus and Klebsiella pneumoniae were identified more in mortality group (p=0.003 for S. aureus, p=0.009 for K. pneumoniae). All viruses were seasonal (i.e., greater prevalence in a particular season; p < 0.050). Influenza virus and rhinovirus were mainly identified in the winter, parainfluenza virus in the summer, and metapneumovirus in the spring. CONCLUSION: This information on the epidemiology of respiratory infections in AECOPD will improve the management of AECOPD using antibiotics and other treatments in Korea.
Anti-Bacterial Agents ; Bacteria ; Epidemiology ; Haemophilus influenzae ; Klebsiella pneumoniae ; Korea ; Medical Records ; Metapneumovirus ; Mortality ; Orthomyxoviridae ; Paramyxoviridae Infections ; Prevalence ; Pseudomonas aeruginosa ; Pulmonary Disease, Chronic Obstructive ; Respiratory Tract Infections ; Rhinovirus ; Seasons ; Staphylococcus aureus ; Streptococcus pneumoniae

PURPOSE: Croup is known to have epidemics in seasonal and biennial trends, and to be strongly associated with epidemics of parainfluenza virus. However, seasonal and annual epidemics of croup have not been clearly reported in Korea. This study aimed to examine the seasonal/annual patterns and etiologies of childhood croup in Korea during a consecutive 6-year period. METHODS: Pediatric croup data were collected from 23 centers in Korea from 1 January 2010 to 31 December 2015. Electronic medical records, including multiplex reverse transcription polymerase chain reaction (RT-PCR) results, demographics and clinical information were cross-sectionally reviewed and analyzed. RESULTS: Overall, 2,598 childhood croup patients requiring hospitalization were identified during the study period. Among them, a total of 927 who underwent RT-PCR were included in the analysis. Males (61.5%) predominated, and most (63.0%) of them were younger than 2 years of age (median, 19 months; interquartile range, 11–31 months). Peak hospitalization occurred in 2010 and 2012 in even-numbered years, and parainfluenza virus (PIV, 39.7%) was the most common cause of childhood croup requiring hospitalization, followed by respiratory syncytial virus (14.9%), human rhinovirus (12.5%), Mycoplasma pneumonaie (10.6%), and human coronavirus (7.3%). CONCLUSION: It is concluded that croup hospitalization has a biennial pattern in even-numbered years. PIV may be the most common cause of childhood croup; however, croup epidemics could be attributed to other viruses.
Child ; Coronavirus ; Croup ; Demography ; Electronic Health Records ; Hospitalization ; Humans ; Korea ; Male ; Mycoplasma ; Paramyxoviridae Infections ; Polymerase Chain Reaction ; Respiratory Syncytial Viruses ; Retrospective Studies ; Reverse Transcription ; Rhinovirus ; Seasons

BACKGROUND: This study investigated the effect of fine dust concentrations in the air on the incidence of viral respiratory infections in the Republic of Korea.METHODS: A time series analysis using R statistics was performed to determine the relationship between weekly concentrations of fine dust in the air and the incidences of acute respiratory tract infections caused by the respiratory syncytial virus (RSV), adenovirus (HAdV), rhinovirus (HRV), human metapneumovirus (HMPV), human coronavirus (HCoV), human bocavirus (HBoV), human parainfluenza virus (HPIV), and influenza virus (IFV), from the beginning of 2016 to the end of 2017. Correlations between various meteorological factors and the amount of fine dust were analyzed using the Spearman's rank correlation coefficient. To analyze the relationship between viral infections and fine dust, a quasi-poisson analysis was performed.RESULTS: The incidence of the HAdV was proportional to fine dust and air temperature. The IFV was proportional to fine dust and relative humidity and was inversely proportional to temperature. The HMPV was proportional to fine dust, wind speed, and inversely proportional to relative humidity. The HCoV was proportional to micro dust, relative humidity, and inversely proportional to temperature. Both the HBoV and HPIV were directly proportional to fine dust, temperature, wind speed, and inversely proportional to relative humidity. The RSV was inversely proportional to fine dust, temperature, wind speed. A lag effect was observed for the influenza virus, in that its incidence increased 2–3 weeks later on the cumulative lag model.CONCLUSION: As the weekly average concentration of fine dust increases, the incidence of HAdV, HMPV, HCoV, HBoV, HPIV, and influenza increase.
Adenoviridae ; Air Pollution ; Coronavirus ; Dust ; Human bocavirus ; Humans ; Humidity ; Incidence ; Influenza, Human ; Metapneumovirus ; Meteorological Concepts ; Orthomyxoviridae ; Paramyxoviridae Infections ; Particulate Matter ; Republic of Korea ; Respiration Disorders ; Respiratory Syncytial Viruses ; Respiratory Tract Infections ; Rhinovirus ; Wind

BACKGROUND: Neutropenia can be easily found in previously healthy children associated with various medical conditions, and the clinical course ranges from transient benign to life threatening. This study aimed to investigate the etiology, clinical characteristics, and clinical courses of neutropenia in previously healthy children. METHODS: We evaluated 215 previously healthy children under aged 18 years who diagnosed with neutropenia in two hospitals. Clinical and laboratory features were analyzed retrospectively based on the medical records. RESULTS: Transient infectious neutropenia (TIN) accounted for 97.7% of cases and chronic neutropenia (CN), for 2.3%. An infectious agent was identified in 128/210 (61%) patients with TIN, and the most frequent agents were viruses (46.5%). The most common viral agent was respiratory syncytial virus (RSV) (29%). TIN subgroups exhibited no differences in severity according to infectious agent (virus, bacteria, Mycoplasma); however, neutropenia severity differed among viral agents [mild-to-moderate neutropenia in the RSV group (857.3±293.3/µL) and moderate-to-severe neutropenia in the parainfluenza group (567.3±198.1/µL); P=0.017]. All patients with CN had anti-neutrophil antibody positivity (autoimmune neutropenia, AIN), and moderate-to-severe neutropenia predominated. The median duration of TIN was 8 days (range, 3–286 days), and it was significantly longer for AIN at 330 days (range, 217–730 days) (P=0.000). The median duration of neutropenia was also different according to each viral agent, with 4 days (range, 3–11 days) for the RSV group and longer durations for 3 other groups (influenza, parainfluenza, other respiratory viruses) (P=0.015). CONCLUSION: Neutropenia in previously healthy children is usually of transient infectious origin, with mild-to-moderate severity, and it resolves spontaneously without complications.
Autoimmune Diseases ; Bacteria ; Child* ; Humans ; Medical Records ; Neutropenia* ; Paramyxoviridae Infections ; Respiratory Syncytial Viruses ; Retrospective Studies ; Tin

PURPOSE: We evaluated the clinical features of croup in children according to viral etiology. METHODS: This study enrolled pediatric patients with croup, who showed positive results on respiratory virus reverse transcriptase polymerase chain reaction performed between January 2012 and December 2017. We retrospectively reviewed the medical records. RESULTS: A total of 179 patients (119 boys and 60 girls) were enrolled with the mean age of 18.9±14.7 months. The viruses commonly identified were parainfluenza, respiratory syncytial virus, rhinovirus, and influenza. Among these 4 viruses, patients with rhinovirus infection showed significantly shorter fever and admission durations. Patients with parainfluenza infection showed significantly lower incidences of epinephrine nebulization and patients with influenza infections showed significantly higher incidences of steroid treatment. CONCLUSION: Clinical manifestations of croup differ according to causative viruses. Further studies should be conducted to evaluate the severity and prognosis of croup according to viral etiology.
Child* ; Croup* ; Epinephrine ; Fever ; Humans ; Incidence ; Influenza, Human ; Medical Records ; Paramyxoviridae Infections ; Prognosis ; Respiratory Syncytial Viruses ; Retrospective Studies ; Reverse Transcriptase Polymerase Chain Reaction ; Rhinovirus

Respiratory infections, which are caused by airborne pathogens, are the most common disease of all ages worldwide. This study was conducted to characterize the airborne respiratory pathogens in the public facilities in Busan, South Korea. A total of 260 public facilities were investigated in 2017, 52 seasonal indoor air from 2 hospitals and 208 indoor air samples from 208 randomly selected daycare centers. Among respiratory pathogen, 8 viral pathogens including human adenovirus (HAdV), human bocavirus (HBoV), human rhinovirus (HRV), human parainfluenza virus (HPIV), human respiratory syncytial virus (HRSV), human metapneumovirus (HMPV), human coronavirus (HCoV) and influenza virus (IFV), and 3 bacterial pathogens including Mycoplasma pneumoniae, Bordetella pertussis, and Chlamydophila pneumoniae, were investigated by multiplex real-time reverse transcription polymerase chain reaction. Pathogens were detected in 9 cases (3.4%). Among 9 positive samples, 6 (2.3%) cases were positive for HBoV and 3 (1.2%) cases were positive for IFV. All the positive cases were detected in daycare centers. Additionally, the concentration of HBoV was determined. In HBoV-positive samples, the cycle threshold (Ct) values of HBoV were 29.73~36.84, which are corresponding to the viral concentration of 4.91 × 10⁰ ~ 9.57 × 10² copies/ml. Serotype distribution of isolated HBoV was analyzed by sequencing of VP1/VP2 gene. All of the HBoV isolates were identified as HBoV type 1 with a high similarity among the isolates (>97%). No bacterial pathogen was identified in indoor air samples. Although virus concentration was not high in public facilities (daycare center), the presence of respiratory viral pathogens has been identified. Effective ventilation and air purification strategies are needed to reduce the indoor concentration of respiratory pathogens. A long-term and ongoing surveillance plan for respiratory pathogen management should be established.
Adenoviruses, Human ; Bordetella pertussis ; Busan ; Chlamydial Pneumonia ; Chlamydophila pneumoniae ; Coronavirus ; Human bocavirus ; Humans ; Korea ; Metapneumovirus ; Mycoplasma pneumoniae ; Orthomyxoviridae ; Paramyxoviridae Infections ; Pneumonia, Mycoplasma ; Polymerase Chain Reaction ; Public Facilities* ; Respiratory Syncytial Virus, Human ; Respiratory Tract Infections ; Reverse Transcription ; Rhinovirus ; Seasons ; Serogroup ; Ventilation