[Parainfluenza virus type 4 infections]

To describe the clinical and epidemiological characteristics of parainfluenza virus type 4 infections in pediatric patients.

Inpatients and outpatients with lower respiratory tract infections were studied. Recorded data were age, sex, clinical diagnosis, temperature, oxygen saturation, chest radiograph and length of hospital stay. Nasopharyngeal aspirates were studied through indirect immunofluorescence, tissue culture and a new multiplex reverse-transcriptase polymerase chain reaction (RT-PCR) able to identify the four types of human parainfluenza virus in the same reaction.

Two hundred thirty specimens from 191 patients were analyzed. Parainfluenza viruses were diagnosed in 35.1 %: 37.3 % type 1, 10.4 % type 2, 38.9 % type 3 and 13.4 % type 4. RNA from parainfluenza virus type 4 was amplified in 10 aspirates from nine patients. Of these, all except one were aged less than two years (range: 26 days to 23 months). The clinical diagnosis was bronchiolitis or wheezing associated with lower respiratory tract infection. Six patients required admission, with a mean oxygen saturation of 89.5 % and a mean length of hospital stay of 7.6 days.

This is the first description of the characteristics of parainfluenza virus type 4 in Spain. Infections associated with this virus are not as mild as previously thought. Application of a multiplex RT-PCR allows identification of respiratory infections due to parainfluenza virus type 4 that would otherwise be underdiagnosed.