[Viral infection of the lower respiratory tract in hospitalized infants: etiology, clinical features and risk factors].

OBJECTIVE

The aim of this study was to assess the clinical and virological characteristics of lower respiratory tract (LRT) infection in hospitalized infants in Spain and to identify clinical, radiological or laboratory parameters that could, on admission, be associated with a more severe clinical course.

METHODS

A prospective study of infants less than 24 months old hospitalized for LRT infection during six consecutive seasons was performed.

RESULTS

A total of 617 infants were included in the study. Diagnosis was bronchiolitis in 64 %, wheezy bronchitis in 24.6 %, laryngitis in 4.4 % and pneumonia in 6.8 %. The mean age was 269 188 days, the male/female ratio was 1:6 and the mean hospital stay was 6.6 3.5 days. At least one viral agent was identified in 55.6 % of the episodes, of which 83.6 % were due to respiratory syncytial virus (RSV). Other less frequently identified viruses were parainfluenza in 7 %, adenovirus in 4.3 % and influenza in 4 %. Coinfection was identified in 6.2 % of RSV-positive infants. These infants were younger (p < 0.005), had higher respiratory distress assessment instrument (RDAI) scores and longer hospital stay than infants in the other etiologic groups. Chest radiographs were performed in 94.3 % of the infants and 39.5 % showed infiltrate or atelectasis. This radiological alteration was significantly associated with a fever of more than 38.5 C and reactive C protein concentrations of more than 30 mg/L (p < 0.001 and p < 0.002), but not with higher RDAI score, SaO2 equal to or less than 87 %, or longer hospital stay. In the crude analysis, hospitalization for more than 5 days was associated with lower age (p < 0.01), a mean RDAI score of more than 6 (p < 0.003), SaO2 equal to or less than 87 % (p < 0.01) and RSV infection (p < 0.001). However, in the multivariate analysis only SaO2 equal to or less than 87 % and RSV infection were significantly associated with prolonged hospitalization.

CONCLUSIONS

The most common lower respiratory tract infections in hospitalized infants in Spain are the various types of RSV-positive bronchiolitis, which have a clinical pattern similar to that described in other countries. Hypoxia on admission and RSV infection are the most important risk factors for prolonged hospitalization.