Background: The coronavirus disease (COVID-19) pandemic is an important health crisis worldwide. Several strategies were implemented to combat COVID-19, including wearing masks, hand hygiene, and social distancing. The impact of these strategies on COVID-19 and other viral infections remains largely unclear. Objective: We aim to investigate the impact of implemented infectious control strategies on the incidences of influenza, enterovirus infection, and all-cause pneumonia during the COVID-19 pandemic. Methods: We utilized the electronic database of the Taiwan National Infectious Disease Statistics System and extracted incidences of COVID-19, influenza virus, enterovirus, and all-cause pneumonia. We compared the incidences of these diseases from week 45 of 2016 to week 21 of 2020 and performed linear regression analyses. Results: The first case of COVID-19 in Taiwan was reported in late January 2020 (week 4). Infectious control strategies have been promoted since late January. The influenza virus usually peaks in winter and decreases around week 14. However, a significant decrease in influenza was observed after week 6 of 2020. Regression analyses produced the following results: 2017, R2=0.037; 2018, R2=0.021; 2019, R2=0.046; and 2020, R2=0.599. A dramatic decrease in all-cause pneumonia was also reported (R2 values for 2017-2020 were 0.435, 0.098, 0.352, and 0.82, respectively). Enterovirus had increased by week 18 in 2017-2019, but this was not observed in 2020. Conclusions: Using this national epidemiological database, we found a significant decrease in cases of influenza, enterovirus, and all-cause pneumonia during the COVID-19 pandemic. Wearing masks, hand hygiene, and social distancing may contribute not only to the prevention of COVID-19 but also to the decline of other respiratory infectious diseases. Further studies are warranted to elucidate the causal relationship.

Respiratory viruses are a common cause of respiratory tract infection (RTI), particularly in neonates and children. Rapid and accurate diagnosis of viral infections could improve clinical outcomes and reduce the use of antibiotics and treatment sessions. Advances in diagnostic technology contribute to the accurate detection of viruses. We performed a multiplex real-time polymerase chain reaction (PCR) to investigate the viral etiology in pediatric patients and compared the detection rates with those determined using traditional antigen tests and virus cultures. Fifteen respiratory viruses were included in our investigation: respiratory syncytial virus A/B (RSV), influenza virus A (FluA) and influenza virus B (FluB), human metapneumovirus (MPV), enterovirus (EV), human parainfluenza virus (PIV) types 1–4, human rhinovirus (RV), human coronavirus OC43, NL63, and 229E, human adenovirus (ADV), and human bocavirus (Boca). In total, 474 specimens were collected and tested. Respiratory viruses were detected more frequently by PCR (357, 75.3%) than they were by traditional tests (229, 49.3%). The leading pathogens were RSV (113, 23.8%), RV (72, 15.2%), PIV3 (53, 11.2%), FluA (51, 10.8%), and ADV (48, 10.1%). For children younger than 5 years, RSV and RV were most prevalent; for children older than 5 years, FluA and ADV were the most frequently detected. Of the specimens, 25.8% (92/357) were coinfected with two or more viruses. RV, Boca, PIV2, FluB, and PIV4 had higher rates of coinfection; MPV and PIV1 had the lowest rates of coinfection (9.1% and 5.3%). To conclude, the detection power of PCR was better than that of traditional antigen tests and virus cultures when considering the detection of respiratory viruses. RSV and RV were the leading viral pathogens identified in the respiratory specimens. One-quarter of the positive specimens were coinfected with two or more viruses. In the future, further application of PCR may contribute to the rapid and accurate diagnosis of respiratory viruses and could improve patient outcomes.

Influenza virus infection is a major global public health problem, and the efficacy of influenza vaccination is not satisfactory. Vitamin D is involved in many immune-mediated inflammatory processes. The impact of vitamin D levels on the immunogenic response to influenza vaccination is not clear. We performed a comprehensive literature search and systematic review of studies that investigated vitamin D and influenza vaccination. Data pertaining to study population, vaccine components, vitamin D levels, and immunogenic response were analyzed. Nine studies, with a combined study population of 2367 patients, were included in the systematic review. Four studies were included in the meta-analysis to investigate the influence of vitamin D deficiency (VDD) on the seroprotection (SP) rates and seroconversion (SC) rates following influenza vaccination. We found no significant association between vitamin D level and the immunogenic response to influenza vaccination. However, strain-specific differences may exist. We observed lower SP rates of influenza A virus subtype H3N2 (A/H3N2) and B strain in VDD patients than patients with normal vitamin D levels (A/H3N2: 71.8% vs. 80.1%, odds ratio (OR): 0.63, 95% confidence interval (CI): 0.43–0.91, p = 0.01; B strain: 69.6% vs. 76.4%, OR: 0.68, 95% CI: 0.5–0.93, p = 0.01). However, the SP rates of A/H1N1 and SC rates of all three strains were not significantly different in VDD and control groups. In conclusion, no association was observed between VDD and immunogenic response to influenza vaccination.

Respiratory syncytial virus (RSV) infection is an important cause of viral respiratory tract infection in children. This retrospective study describes the clinical characteristics of severe RSV infection and determines the risk factors for death. Patients were identified through a review of all patients discharged with a diagnosis of RSV lower respiratory tract infection and admitted to hospital in the pediatric intensive care unit (PICU) of a tertiary medical center between July 1, 2001 and June 30, 2010. The medical and demographic variables were recorded and analyzed. The 186 RSV-positive patients admitted to the PICU had a median age of 5.3 months (interquartile range 2.3-12.4 months) and included 129 boys and 57 girls. Among them, 134 had at least one underlying disease: prematurity in 92, neurological disease in 57, bronchopulmonary dysplasia in 40, congenital heart disease in 26, hematological malignancies in 11, and Down's syndrome in nine patients. The 10 patients who died from RSV-related causes had a median age of 20.8 months (interquartile range 6.6-89.2 months) and all had a comorbidity. In multivariate analysis, the risk factors for death in severe RSV infection were Down's syndrome (odds ratio 7.20, 95% confidence interval 1.13-45.76; p = 0.036) and nosocomial RSV infection (odds ratio 4.46, 95% confidence interval 1.09-18.27; p = 0.038). Down's syndrome and nosocomial RSV infection are significantly associated with death in severe RSV infections. Clinicians should be alert to these conditions.

The purpose of this study was to determine the pathogens and to estimate the incidence of pediatric community-acquired pneumonia (CAP) in Taiwan. This prospective study was conducted at eight medical centers from November 2010 to September 2013. Children aged 6 weeks to 18 years who met the radiologic criteria for pneumonia were enrolled. To detect classical and atypical bacteria and viruses, blood and pleural fluids were cultured, and respiratory specimens were examined by multiple conventional and molecular methods. At least one potential pathogen was identified in 705 (68.3%) cases of 1032 children enrolled, including bacteria in 420 (40.7%) cases, virus in 180 (17.4%) cases, and mixed viral-bacterial infection in 105 (10.2%) cases. Streptococcus pneumoniae (31.6%) was the most common pathogen, followed by Mycoplasma pneumoniae (22.6%). Adenovirus (5.9%) was the most common virus. RSV was significantly associated with children aged under 2 years, S. pneumoniae in children aged between 2 and 5 years, and M. pneumoniae in children aged >5 years. The annual incidence rate of hospitalization for CAP was highest in children aged 2–5 years (229.7 per 100,000). From 2011 to 2012, significant reduction in hospitalization rates pertained in children under 5 years of age, in pneumonia caused by pneumococcus, adenovirus or co-infections and complicated pneumonia. CAP related pathogens have changed after increased conjugated pneumococcal vaccination rates. This study described the latest incidences and trends of CAP pathogens, which are crucial for prompt delivery of appropriate therapy.

Respiratory syncytial virus (RSV) is a leading cause of acute lower respiratory tract infection in young children and the second leading cause of infant death worldwide. While global circulation has been extensively studied for respiratory viruses such as seasonal influenza, and more recently also in great detail for SARS-CoV-2, a lack of global multi-annual sampling of complete RSV genomes limits our understanding of RSV molecular epidemiology. Here, we capitalise on the genomic surveillance by the INFORM-RSV study and apply phylodynamic approaches to uncover how selection and neutral epidemiological processes shape RSV diversity. Using complete viral genome sequences, we show similar patterns of site-specific diversifying selection among RSVA and RSVB and recover the imprint of non-neutral epidemic processes on their genealogies. Using a phylogeographic approach, we provide evidence for air travel governing the global patterns of RSVA and RSVB spread, which results in a considerable degree of phylogenetic mixing across countries. Our findings highlight the potential of systematic global RSV genomic surveillance for transforming our understanding of global RSV spread.