The Epidemiology And Correlation Between Viral Loads And Genetic Mutations Of Human Bocavirus 1 In 2707 Hospitalized Children With Acute Lower Respiratory Tract Infections

Objective: To analyze the correlation among the viral loads, genetic mutation and clinical manifestation in children with acute lower respiratory tract infection.Methods: NPAs were collected from 2707 hospitalized children diagnosed with LRTI in the Department of Respiratory Medicine at the Children’s Hospital of Chongqing Medical University between June 2011 and August 2014. HBo V1 viral loads were tested by Real-Time PCR. For positive cases, NP1 segment were amplified by traditional PCR and sequenced by Shanghai Majorbio Bio-Pharm Technology. Comparing the sequence between NP1 and the HBo V1 standard strain with MAGA.7 software. Analyze the correlation among HBo V1 viral loads, nucleotide mutation and clinical manifestation. Retrospective analysis of PICU patients’ viral loads genetic mutation and clinical characteristics. Data analysis was accomplished by SPSS 19.0 software.Results: There were 383 HBo V1 positive cases(14.3%). The viral loads of all samples are from 1.09*101copies/ml to 5.0*1010copies/ml. 93 samples were sequenced, among which NP1-G236 A nucleotide mutation declared to happen in 17 cases. The viral loads showed no statistic difference between the mutation group and non-mutation group, and between single detection and co-detection group. 3 cases in mutation group were diagnosed with severe lower respiratory infections(17.6%), however there showed no statistic difference of the clinical manifestation between the mutation group and non-mutation group. In clinical manifestation, significant differences of wheezing(63.5% vs. 47.5%, P=0.003), expectoration(78.9% vs. 69.1%, P=0.041), fever(41.5% vs. 28.5%, P=0.01), and elevated WBC(72.3% vs. 54.2%, P=0.001) were recorded between high viral load and low viral load groups. However, the viral loads showed no difference between s LRTI group and non- s LRTI group(χ2=1.69,P=0.69). Infection with high viral loads of HBo V1 won’t increase the possibility of being transferred to PICU(P=0.06), but the possibility of needing mechanical ventilation in high viral loads with co-infections patients is high than that in low viral loads with co-infections patients(4.2% vs. 0,P=0.01).Conclusion: HBo V1 is one of the most important etiology cause of ALRTI inpatients in Chongqing. Patients with high viral loads are more prevalent to have wheezing, expectoration and fever. The NP1 genetic mutation by now showed no influence on the clinical manifestation and viral loads. The viral loads between s LRTI patients and non-s LRTI patients have no difference, or between PICU patients and non- PICU patients. However, high viral loads with co-infections patients are more likely to need mechanical ventilation.