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Objective To understand human rhinovirus (HRV) etiology of acute lower respiratory tract infection (ALRTI) in children in Shanghai area and establish a nested reverse transcription- polymerase chain reaction (nested RT-PCR) assay.Methods Three hundred and forty-two naso- pharyngeal secretion (NPS) samples from ALRTI cases who were hospitalized were collected during January 2005—December 2005.Nested RT-PCR techniques were used to detect HRV-specific RNA.The PCR products were sequenced and data of nucleotides were analyzed.The proportion of HRV infection in children with ALRTI,the distribution of gender,age and season,and clinical char- acteristics were also investigated.Results Forty-six (13.5%) of 342 samples were HRV positive detected by nested RT-PCR.The sequences of 15 positive samples shared high homology of 83%- 97% with HRV sequence in GenBank.Within the 15 positive samples,nucleotide homology varied from 64.4% to 98.4%,and the ratio of genetic variation was from 1.6% to 48.3%./00.These 15 ampli- cons attribute to the two branches of HRV cladogram.The sequences of 15 amplieons were highly varied,in which single nucleotide mutation and several nearby nueleotides mutations were found. Ribonucleotide deletion and insertion in the nucleotide sequence was also found.HRV positive sam- ples were detected in 33 boys and 13 girls,respectively.The ratio of infection cases between boys and girls was 2.5:1.Of 46 HRV infected cases,27 (58.7%) were less than 12 months of age and 38 (82.6%) were less than 3 years old.HRV infected ALRTI occured all the year round and peaked from March to May.Of the patients whose NPS samples were HRV positive detected by nested RT-PCR,45 patients were diagnosed with bronchopneumonia and 1 was diagnosed with asthmatic bronchitis.Fever of most patients was moderate.The peripheral blood leukocyte counts in thirty-nine (84.8%) patients were less than 10?10~9/L.Neutrophil percentages in thirty-seven (80.4%) patients were less than 0.50.C-reactive protein of thirty-six (78.3%) patients were less than 8 mg/L. All of these features were the characteristics of viral pneumonia.The complications were not common and conditions of most patients were not severe.All the children were cured.Conclusions This nes- ted RT-PCR technique is highly specific,rapid and convenient for the detection of HRV RNA in NPS of patients with ALRTI and the genome of HRV viruses is highly variable.The incidence of HRV infection predominates in children in Shanghai area.ALRTI of HRV is short of specificity and condi- tions of most patients are not severe and their prognoses are fine.