Background: Human parainfluenza viruses (HPIVs) are important causes of upper respiratory tract illness (URTI) and lower respiratory tract illness (LRTI). To analyse epidemiologic and clinical characteristics of the four types of human parainfluenza viruses (HPIVs), patients with acute respiratory tract illness (ARTI) were studied in Guangzhou, southern China.Methods: Throat swabs (n=4755) were collected and tested from children and adults with ARTI over a 26-month period, and 4447 of 4755 (93.5%) patients’ clinical presentations were recorded for further analysis.Results: Of 4755 patients tested, 178 (3.7%) were positive for HPIV. Ninety-nine (2.1%) samples were positive for HPIV-3, 58 (1.2%) for HPIV-1, 19 (0.4%) for HPIV-2 and 8 (0.2%) for HPIV-4. 160/178 (88.9%) HPIV-positive samples were from paediatric patients younger than 5 years old, but no infant under one month of age was HPIV positive. Seasonal peaks of HPIV-3 and HPIV-1 occurred as autumn turned to winter and summer turned to autumn. HPIV-2 and HPIV-4 were detected less frequently, and their frequency of isolation increased when the frequency of HPIV-3 and HPIV-1 declined. HPIV infection led to a wide spectrum of symptoms, and more “hoarseness” (p=0.015), “abnormal pulmonary breathing sound” (p<0.001), “dyspnoea” (p<0.001), “pneumonia” (p=0.01), and “diarrhoea” (p<0.001) presented in HPIV-positive patients than HPIV-negative patients. 10/10 (100%) HPIV-positive adult patients (≥14 years old) presented with systemic influenza-like symptoms, while 90/164 (54.9%) HPIV-positive paediatric patients (<14 years old) presented with these symptoms (p=0.005). The only significant difference in clinical presentation between HPIV types was “Expectoration” (p<0.001). Co-infections were common, with 33.3%–63.2% of samples positive for the four HPIV types also testing positive for other respiratory pathogens. However, no significant differences were seen in clinical presentation between patients solely infected with HPIV and patients co-infected with HPIV and other respiratory pathogens.Conclusions: HPIV infection led to a wide spectrum of symptoms, and similar clinical manifestations were found in the patients with four different types of HPIVs. The study suggested pathogenic activity of HPIV in gastrointestinal illness. The clinical presentation of HPIV infection may differ by patient age.

Background: Human bocavirus (HBoV) is a newly discovered parvovirus associated with acute respiratory tract illness (ARTI) and gastrointestinal illness. Our study is the first to analyze the characteristics of HBoV-positive samples from ARTI patients with a wide age distribution from Guangzhou, southern China.Methods: Throat swabs (n=2811) were collected and analyzed from children and adults with ARTI over a 13-month period. The HBoV complete genome from a 60 year-old female patient isolate was also determined.Results: HBoV DNA was detected in 65/2811 (2.3%) samples, of which 61/1797 were from children (<18 years old) and 4/1014 from adults (≥18 years old). Seasonal peaks of 4.8% and 7.7% were detected in May and June, respectively. 28 of 65 (43.1%) HBoV-positive samples were co-detected with 11/16 other potential pathogens.Mycoplasma pneumoniaehad the highest frequency of 16.9% (11/65). Upper and lower respiratory tract illness were common symptoms, with 19/65 (29.2%) patients diagnosed with pneumonia by chest radiography. All four adult patients had systemic influenza-like symptoms. Phylogenetic analysis of the complete genome revealed a close relationship with other HBoVs, and a more distant relationship with HBoV2 and HBoV3.Conclusions: HBoV was detected from children and adults with ARTI from Guangzhou, southern China. Elderly people were also susceptive to HBoV. A single lineage of HBoV was detected among a wide age distribution of patients with ARTI.

Background: Human Adenoviruses (HAdVs) cause a wide array of illnesses in all age groups. They particularly cause frequent morbidity among children. In China, human adenovirus types 3, 4, 7, 11, 14, 21, and 55 have caused at least seven outbreaks since 2000. However, limited studies are available regarding the epidemiological patterns and diversity of HAdVs types among hospitalized patients with respiratory tract infections (RTIs). Methods: To understand the epidemiology and subtype distribution of HAdV infections associated with RTIs in China, nasal swab (NS) clinical samples were collected from 4129 patients in a Guangzhou hospital between August 2017 and October 2019. PCR, sequencing, and phylogenetic analysis were performed on these specimens to identify HAdV subtypes. Results: HAdV was successfully sequenced in 99 (2.4%) of the 4129 NS specimens, with the highest HAdV prevalence (6.3%) found in children between the ages of 5 and 10 years. Among HAdV-positive specimens, the most prevalent genotypes identified were HAdV-B3 (55.6%) and HAdV-B7 (25.3%). The most common symptoms in the HAdV-infected patients were fever (100%), cough (80.8%), and rhinorrhea (71.8%). HAdV infections were detected throughout the year with a relatively higher prevalence in summer. Conclusion: All ages suffer adenovirus infections, but young children are at the greatest risk. This study data demonstrates that at least three species of HAdVs (species B, C, and E) are circulating in Guangzhou City, China. As antiviral therapies and type-specific vaccines become available, such epidemiological data will be useful in guiding therapy and public health interventions.

Background: Human respiratory syncytial virus (RSV) is a leading cause of acute lower respiratory tract infection and hospitalization, especially in children. Highly mutagenic nature and antigenic diversity enable the RSV to successfully survive in human population. We conducted a molecular epidemiological study during 2017–2021 to investigate the prevalence and genetic characteristics of RSV. Methods: A total of 6499 nasopharyngeal (NP) swabs were collected from hospitalized children at Department of Pediatrics, Guangdong Provincial Hospital of Traditional Chinese Medicine, Guangzhou, Guangdong, China. All NP swab specimens were preliminary screened for common respiratory viruses and then tested for RSV using specific PCR assays. Partial G genes of RSV were amplified for phylogenetic analysis and genetic characterization. Results: The overall detection rate for common respiratory viruses was 16.12% (1048/6499). Among those, 405 specimens (6.20%, 405/6499) were found positive for RSV. The monthly distribution of RSV and other respiratory viruses was variable, and the highest incidence was recorded in Autumn and Winter. Based on the sequencing of hypervariable region of G gene, 93 RSV sequences were sub-grouped into RSV-A (56, 60.2%) and RSV-B (37, 39.8%). There was no coinfection of RSV-A and RSV-B in the tested samples. Phylogenetic analysis revealed that RSV-A and RSV-B strains belonged to ON1 and BA9 genotypes respectively, indicating predominance of these genotypes in Guangzhou. Several substitutions were observed which may likely change the antigenicity and pathogenicity of RSV. Multiple glycosylation sites were noticed, demonstrating high selection pressure on these genotypes. Conclusion: This study illustrated useful information about epidemiology, genetic characteristics, and circulating genotypes of RSV in Guangzhou China. Regular monitoring of the circulating strains of RSV in different parts of China could assist in the development of more effective vaccines and preventive measures.

Background Human respiratory syncytial virus (RSV) is a leading cause of acute lower respiratory tract infection and hospitalization, especially in children. Highly mutagenic nature and antigenic diversity enable the RSV to successfully survive in human population. Regular monitoring of the circulating strains of RSV in different parts of China could assist in the development of more effective vaccines and preventive measures. We performed a molecular epidemiological study during 2017–2021 to investigate the prevalence and genetic characteristics of RSV in China. Methods A total of 6499 nasopharyngeal (NP) swabs were collected from patients suffering from respiratory infections at Department of Pediatrics, Guangdong Provincial Hospital of Traditional Chinese Medicine, Yuexiu District, Guangzhou, Guangdong, China. Results Overall detection rate for respiratory viruses was 16.12% (1048/6499). A total of 405 specimens (6.20%, 405/6499) were found positive for RSV. Seasonal distribution of RSV and other respiratory viruses was variable and highest incidence were recorded in winter. Based on sequencing of hypervariable region of G gene, 93 RSV sequences were sub-grouped into RSV-A (56, 60.2%) and RSV-B (37, 39.8%). There was no coinfection of RSV-A and RSV-B in tested samples. Phylogenetic analysis revealed that RSV-A and RSV-B strains belonged to ON1 and BA9 genotype respectively, indicating predominance of these genotypes in Guangzhou. Deduced amino acid sequence analysis determined several substitutions which may likely change antigenicity and pathogenicity of RSV. Multiple glycosylation sites were observed in the second hypervariable region of the G protein, demonstrating high selection pressure on these genotypes. Conclusion This study illustrated the useful information about epidemiology, genetic characteristics and circulating genotypes of RSV in Guangzhou China which may facilitate policy makers, clinicians, and researchers for a better understanding of the evolution of RSV within and outside of China. Due to emergence of several lineages of ON1 and BA9 genotypes, it is quite possible that new lineages could emerge in near future due to highly mutagenic nature of RSV. Continuous and long-term surveillance programs coupled with clinical data must be initiated in Guangzhou to better understand the pattern of seasonal distribution of circulating genotypes of RSV and find any association between emerging genotypes and disease severity.

Background: Community-acquired pneumonia (CAP) is a common infectious disease with a mortality rate of 2–14%. Respiratory syncytial virus (RSV) frequently causes CAP in children. This study aimed to investigate RSV genetic diversity in children under 15 years of age with CAP, evaluate nucleotide substitution rates, and examine associations with clinical characteristics and outcomes. Methods: A retrospective observational study was conducted using nasal swab samples collected from children under 15 years of age diagnosed with CAP. RSV identification involved cell culture and immunofluorescence microscopy, followed by molecular analyses using qPCR, nested PCR, and Sanger sequencing. Bioinformatics tools were applied to assess phylogenetics, evolutionary trends, genetic distance, and nucleotide substitution rates. Statistical analysis of clinical and laboratory data was performed to identify correlations between RSV features and patient characteristics. Results: Among 346 CAP cases, RSV was detected in 26.88%, with the highest prevalence in children aged 1–2 years. Subtype A exhibited higher nucleotide substitution rates than subtype B. Shortness of breath and high fever were significantly associated with increased nucleotide diversity. RSV infections peaked in winter, particularly in 2018 and 2019. Elevated substitution rates were linked to longer hospital stays, greater risk of complications such as secondary bacterial infections, and increased RSV-related morbidity. Conclusion: RSV higher nucleotide substitution rates, especially in children under 3 years of age, were associated with more severe clinical outcomes and prolonged hospitalization. Phylogenetic analysis indicated distinct evolutionary patterns, with subtype B exhibiting a more rapid evolutionary rate than subtype A. Impact: This study highlights the high prevalence of respiratory viruses, particularly respiratory syncytial virus (RSV), in children with community-acquired pneumonia in Guangzhou. It provides detailed molecular epidemiological data on RSV, including genetic variation patterns and evolutionary rates. The findings contribute regional data essential for epidemiological research and public health planning in similar geographic areas. These results support clinical decision-making and inform public health strategies, particularly those focused on RSV vaccination and infection control.