According to the World Health Organization (WHO) 20% of hospitalizations of children under 5 years are attributable to severe acute respiratory illness. Acute respiratory infections account for around 2% of the total deaths every year in children under 5 years in Austria1. Respiratory syncytial virus (RSV) is a common causative agent of respiratory infections responsible for bronchiolitis, pneumonia and other respiratory problems in people of all ages, but it is of particular importance for inducing severe lower respiratory tract infection in infants. For this study, respiratory samples were taken from children under age of 5 years, during 2015. We first investigated the presence of multiple respiratory infections in these children and compared four different multiplex PCR tests: RespiFinder (Qiagen), an In-house PCR, R-gene (BioMérieux) and Respiratory Pathogen 21 (Fast track diagnostics-FTD). Since FTD was the best option, we used this kit to test all obtained samples. All RSV positives samples were further subtyped and the G protein was sequenced. We could observe that 42%, 36.4% and 21.6% were infected with just one pathogen (single infection), with more than one pathogen (multiple infection) or were negative, respectively. RSV was the major infectious pathogen, being present in 40.7% of the samples. A 41.3% was RSV-A and 54.3% was RSV-B infection, respectively. Two samples could not be subtyped. Twice as much RSV-A virus was detected in single infections. Association with clinical data revealed that multiple infections seem to be related with severe illness, while single RSV infections were present in both severe and milder forms. We could observe that RSV-A seem to be related with pneumonia and children older than 3 month. RSV-B seemed to be associated with Bronchiolitis in children with 3 month or younger. ^Phylogenetic analysis of nucleotide sequence of G protein revealed that all RSV-A contained a 72 nucleotide mutation in the G protein and in RSV-B a 60 nucleotide duplication was found.
These mutations in RSV G protein, together with some patient characteristic like age or gender could be the explanation of the severe form observed during 2015. Further investigations of the duplication are necessary to determine an association of the observed mutations with the severity of the infection.