Clinical features and molecular characteristics of influenza B viral pneumonia in elderly patients in Nanjing city

Objective To analyze the clinical features of influenza B viral pneumonia among elderly patients and the molecular characteristics of the virus, so as to provide the basis for clinical diagnosis and treatment as well as disease prevention. Methods The respiratory tract samples were collected from hospitalized elderly patients with pneumonia in the Nanjing First Hospital from December, 2017 to March, 2018. Fluroscent quantitative RT-PCR was used in the nucleic acids testing for the screening of influenza B infection cases. The clinical data of the cases were collected. The whole genomes of influenza B virus were sequenced by high-throughput sequencing. Analyses of molecular characteristics for HA and NA were carried out by bioinformatic methods. Results For the 20 patients, 85% of them had at least one underlying disease. Lesions in both lungs were found in 70% of the patients, and the case fatality rate was 25%. The differences in the peripheral blood lymphocyte percentage and total serum bilirubin between death patients and survived patients were statistically significant (P<0.05). The results of sequence analysis for the 17 strains influeuza B showed that 16 strains were belong to Yamagata lineage while 1 strain was in Victoria lineage. The NA gene of the strain in Victoria lineage was originated from the Yamagata lineage, indicating that reassortments may occur. Conclusions Most of the elderly patients with influenza B virus infection were combined with underlying diseases. Decreased peripheral blood lymphocytes percentage indicated poor prognosis. Both Yamagata and Victoria lineages were detected in elderly patients infected by influenza B virus, and stains in Yamagata lineage were predominant. Key words: Elderly; Influenza B virus; Pneumonia; Clinical features; Molecular characteristics