Characterisation of RSV infections in children without chronic diseases aged 0-36 months during the post-COVID-19 winter season 2022/2023.

Background: Respiratory syncytial virus (RSV) is one of the leading causes of hospitalisation, morbidity, and mortality due to respiratory infection in the first years of life. This longitudinal prospective study outlines the 2022/23 season's viral patterns in Austria after the epidemiological changes determined by public health measures. We aimed to highlight differences within the RSV subtypes and genotypes in 0-36-month-old children without chronic diseases in the outpatient setting. Methods: From November 2022 to March 2023 children younger than 36 months admitted to Vienna's largest paediatric primary healthcare centre with an acute respiratory infection were enrolled in this study. Nasal swabs and multiplex PCR panels detected 20 viruses including RSV subtypes and genotypes. Clinical presentation, features, and treatment of the participants were documented and analysed using the Modified Tal Score (MTS). Patients were scheduled for a telemedical follow-up one week after the initial appointment. Analysis was done using descriptive statistics, including Cramér V and binominal logarithmic regression. Results: Among the 345 samples from 329 children, RSV was the most common virus (31.9%), followed by influenza (17.5%) and rhinovirus infections (20.58%). Of the RSV positive samples, only 13 cases were RSV subtype A (11.8%), whereas 97 were of subtype B (87.3%); ON1 and BA9 were the only detectable RSV genotypes (ON1: BA9 = 1:9.25). RSV was the main predictor of hospitalisation (OR: 7.5, 95% CI: (1.46-38.40), and age had a significant but smaller effect (OR: 0.89, 95% CI: (0.81-0.99). Almost all patients' clinical status improved within the first days. Conclusion: RSV cases showed a rapid onset in late November 2022, and subtype B was predominant throughout the season. RSV infection was associated with higher hospitalisation rates, even after excluding high-risk patients (preterm and severe chronic diseases population).Further testing in the upcoming winter seasons will improve our knowledge of the dominant subtype and its association with disease severity, especially with the development of novel RSV vaccine candidates.

The surge of RSV and other respiratory viruses among children during the second COVID-19 pandemic winter season.

Background: The non-pharmaceutical measures in the first Covid-19 winter season significantly impacted respiratory pathogens such as RSV, influenza, or metapneumovirus, which cause respiratory infections, especially in infants and young children. This longitudinal prospective study aimed to determine how less strict measures affect the pathogen profile in the second winter season. Methods: From September 2021 till the end of March 2022, 678 children (0-36 months) admitted to Vienna's largest pediatric center with an acute respiratory infection were enrolled in this study. The researchers performed nasal swabs and tested them by multiplex PCR for 23 respiratory pathogens, chronicled clinical features and treatment, and analyzed the effect of lockdown on the pathogen prevalence. Results: The 815 smears of 678 children revealed the most common pathogens to be rhino-/enterovirus (38.5%), RSV (26.7%), and metapneumovirus (7.2%). The lockdown interrupted the early RSV onset in September [RR 0.367, CI (0.184-0.767), p = 0.003], while no effects on the other pathogens were found. Metapneumovirus started circulating in January. Influenza was only sporadically detected. The hospitalization rate was significantly higher than last season due to RSV [OR 4.089, 95%CI (1.414-11.827), p-adj = 0.05]. Conclusion: With more flexible non-pharmaceutical measures, children aged 0-36 months started presenting again with viral pathogens, such as RSV and metapneumovirus. RSV, associated with a high hospitalization rate, had a very early onset with an abrupt interruption due to the only lockdown.

Respiratory Infections in Children During a Covid-19 Pandemic Winter.

Background: The Covid-19 pandemic compelled the implementation of measures to curb the SARS CoV-2 spread, such as social distancing, wearing FFP2 masks, and frequent hand hygiene. One anticipated ramification of these measures was the containment of other pathogens. This prospective, longitudinal study aimed to investigate the spread of 22 common seasonal non-SARS-CoV-2 pathogens, such as RSV and influenza, among children with an acute respiratory infection during a pandemic. Methods: Three hundred ninety children (0-24 months) admitted to Vienna's largest pediatric center with acute respiratory infection (November 2020-April 2021) were included in this study. The researchers tested nasal swabs for 22 respiratory pathogens by Multiplex PCR, documented clinical features and treatment, and evaluated data for a potential connection with the lockdown measures then in force. Results: The 448 smears revealed the most common pathogens to be rhino-/enterovirus (41.4%), adenovirus (2.2%), and coronavirus NL63 (13.6%). While the first two were active throughout the entire season, coronaviruses peaked in the first trimester of 2021 in conjunction with the lift of the lockdown period (OR 4.371, 95%CI 2.34-8.136, P < 0.001). RSV, metapneumovirus, and influenza were absent. Conclusion: This prospective, longitudinal study shows that Covid-19 measures suppressed the seasonal activity of influenza, RSV, and metapneumovirus among very young children, but not of rhino-/enterovirus and adenovirus. The 0-24 month-olds are considered the lowest risk group and were only indirectly affected by the public health measures. Lockdowns were negatively associated with coronaviruses infections.