OBJECTIVETo understand the relationship of parainfluenza virus (PIV) and acute respiratory infections in infants and young children in Beijing, occurred in recent years.

METHODS3141 throat swab/nasopharyngeal aspirate specimens were collected from infants and young children with acute respiratory tract infections in Beijing from Jan 2001 to Dec 2003. All of these 3141 specimens were inoculated into MDCK cells for influenza virus and PIV isolation, since PIV had been isolated in MDCK cells in this laboratory from preliminary studies. Out of 3141 specimens, 702 were inoculated into MDCK as well as Vero cells to compare the sensitivity on virus isolation of these cell lines by micro plate method. Growth of PIV in cell culture were identified by haemoagglutination test and indirect immunofluorescent assay.

RESULTSThe PIV positive cases in Vero cells were also positive in MDCK cells, indicating that the sensitivity for PIV isolation in MDCK was equal to Vero cells. Out of these 3141 specimens, 94 (3.0%) were PIV positive, including 35 (35/1191, 2.9%) of PIV1, 11 (11/1191, 0.9%) of PIV3 in upper respiratory tract infections; 15 (15/1634, 0.9%) of PIV1, 24 (24/1634, 1.5%) of PIV3 in lower respiratory tract infections; 3 (3/207, 1.4%) of PIV in asthma; 1 (1/38) of PIV in patients with fever; 5 (5/71) of PIV in others. Data indicated that among upper respiratory tract infections caused by PIV, PIV1 was more commonly seen than PIV3.

CONCLUSIONMDCK cells could be used for PIV isolation from clinical samples while PIV was one of the important pathogenic viruses causing acute respiratory tract infections in infants and young children in Beijing for the recente years.