Diagnosis and clinical significance of parainfluenza virus infections in children.

The diagnosis and clinical features of parainfluenza virus infections are described in 151 children admitted to hospital over a 2-year period. Immunofluorescence was the most sensitive method of laboratory diagnosis, while virus isolation in tissue culture was more often achieved from nasopharyngeal secretions than from cough/nasal swabs. Parainfluenza viruses were responsible for approximately 9% of 1603 acute respiratory admissions. Croup was the commonest of the wide range of respiratory illnesses associated with these infections; in a series of 132 children with croup, a parainfluenza virus was identified in 42%. 24 of the 151 children presented with febrile convulsions, and in a series of 209 children admitted with febrile convulsions, parainfluenza viruses were responsible for 11%. 3 of the children died in hospital with their parainfluenza virus infections, and in addition there was one instance of a close association between parainfluenza virus type 3 infection and the sudden unexpected death of an infant at home. Parainfluenza virus types 4a and 4b, which have so far rarely been identified, were isolated from 16 children. The age distribution and seasonal patterns of the infections are described. Attention is drawn to the risks of cross-infection by parainfluenza viruses in children's wards, and the finding that virus is commonly excreted for at least a week after the onset of the illness.