Acute respiratory infections (ARI) account for a large part of all pediatrician visits. Quantitative real-time analysis of the polymerase chain reaction (PCR) has shown great sensitivity in determining viral nucleic acids, but so far it has not been clear which viruses contribute to the development of infections acute respiratory disease in children because many viruses were also detected in small patients without clinical symptoms of respiratory tract infection (PID).

The purpose of the Swedish study was to compare the final diagnostic results using PCR diagnostics in children with IDP versus healthy asymptomatic children who were the control group.

Nasopharyngeal aspirations have been obtained in children with PDI under 5 years of age with PDI and in patients of the same age without symptoms of PDI during the period outside the influenza epidemic (a total of 209 children in each group was examined). The samples were analyzed using PCR diagnostics to determine 16 viruses.

Respiratory viruses were detected in 72.3% of children with IDP (n = 151) and in 35.4% (n = 74) of children in the control group (p = 0.001). Rhinoviruses were found to be the most frequently isolated pathogen in both IDP patients and healthy children in the control group (47.9% and 21.5%, respectively). Metapnevmovirus, parainfluenza virus and respiratory syncytial virus were significantly more likely to be distributed in the group of children with acute respiratory infections compared to the control (parainfluenza virus 7.7% vs 0.5%, PC virus 5.3% vs 0.5% and metapneumovirus 4.8% vs 1.0%).

Infections caused by metapneumoviruses have been characterized by a severe course of the disease with fever, decreased oxygen saturation, shortness of breath and tachycardia.

The bocavirus was assigned much more often in patients with PDI (15.8% vs 4.3%) even after adjusting for co-infection with other viruses and was associated with a severe course of the disease (tachycardia, shortness of breath and cough). Enteroviruses and coronaviruses were often found also in patients with acute respiratory infections and in the control group.

Thus, respiratory syncytial virus, metapneumovirus and parainfluenza virus are the most common etiological factors of acute respiratory infections in children. The definition of other respiratory viruses should be interpreted with caution in relation to the high frequency of detection of the same viruses in children without the clinical symptoms of IDA.