Background: Human Parainfluenza Viruses (HPIV) type 4 are responsible for respiratory infections. Unlike HPIV types 1-3, they are associated with mild infections and appear to be infrequent. Thus, they often go undetected.
Study design: From 1998 to 2002, in 20 respiratory samples of hospitalised patient, we isolated viruses presenting a large syncytial cytopathic effect when inoculated on LLC-MK2 cells. Most of the patients (16/20) were young infants and all of them presented with respiratory infections.
Results: We detected 18 cases during autumn and winter, 1 case during spring and 1 during summer. We could not identify these viruses using the panel of routine assays. Samples were then analysed by specific HPIV 4 RT-PCR and IF assays. All the samples were scored positive with both methods.
Conclusion: We conclude that HPIV 4 infections are probably underestimated. Their role in viral respiratory infections should be carefully investigated using techniques adapted to their detection and culture.