Pulmonary Function and Clinical Manifestations of Patients Infected with Mild Influenza A Virus Subtype H1N1: A One-Year Follow-Up

RESEARCH ARTICLE Pulmonary Function and Clinical Manifestations of Patients Infected with Mild Influenza A Virus Subtype H1N1: A One-Year Follow-Up Wei Liu, Liping Peng, Hongmei Liu, Shucheng Hua* Department of Respiratory Medicine, First Hospital, Jilin University, Changchun, 130021, Jilin Province, China * a11111 Abstract Objective To investigate the long-term effects of mild H1N1 influenza infection on the pulmonary function of a cohort of patients. OPEN ACCESS Citation: Liu W, Peng L, Liu H, Hua S (2015) Pulmonary Function and Clinical Manifestations of Patients Infected with Mild Influenza A Virus Subtype H1N1: A One-Year Follow-Up. PLoS ONE 10(7): e0133698. doi:10.1371/journal.pone.0133698 Editor: Juan C. de la Torre, The Scripps Research Institute, UNITED STATES Methods Forty-eight patients, all diagnosed with influenza A virus subtype H1N1 in 2009, were retrospectively included in this study. Each patient in the study was monitored for 11-13 months by standard pulmonary function examination. The examination included monitoring respiratory tract infection symptoms (cough, expectoration or gasping) and vital signs. Long-term changes in symptoms and changes in vital signs were correlated back to and compared with the severity of the initial H1N1 influenza infection. Received: March 13, 2015 Accepted: June 12, 2015 Published: July 28, 2015 Copyright: © 2015 Liu et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Results One year post discharge, mild to moderate pulmonary dysfunction was observed in the majority of patients. Further, 54.2% of patients had signs of severe abnormal pulmonary function, including diffusion disorder (33.3%) and small airway dysfunction (33.3%). Fourteen patients presented with respiratory tract infection symptoms; 12 with abnormal pulmonary function and two with normal pulmonary function. Our results indicated that the change in pulmonary function at one year post discharge was not significantly correlated with the severity of H1N1 influenza. Data Availability Statement: All relevant data are within the paper. Funding: The authors have no support or funding to report. Competing Interests: The authors have declared that no competing interests exist. Conclusion Signs and symptoms of abnormal pulmonary function accompanied by respiratory tract infection symptoms remain for some patients after one year following discharge from the hospital for mild influenza A virus subtype H1N1 infection. These patients should continue PLOS ONE | DOI:10.1371/journal.pone.0133698 July 28, 2015 1/6 H1N1 Virus Influences with Respiratory Systems to be monitored for any changes in condition and symptoms and rehabilitation treatment should be provided when necessary. Introduction Influenza A virus subtype H1N1, a pandemic 2009 strain, caused widespread outbreaks of influenza in humans. As of 17 June 2010, more than 214 countries had reported confirmed cases of infection with pandemic 2009 influenza A (H1N1) virus [1]. Patients typically presented with severe pneumonia and acute respiratory distress syndrome (ARDS), which led to severe lung damage and in some cases death. After recovery from severe pneumonia and ARDS, various degrees of lung lesions occur, having an impact on patients’ respiratory function and in turn his or her quality of life. In this study, we examined the pulmonary function of patients infected with influenza A virus subtype H1N1 one year after hospitalization for the infection. These results provide valuable information for future diagnosis and rehabilitation treatment of H1N1 and other pandemic or severe influenza strain infections. Materials and Methods Subjects A one-year pulmonary function follow up of was performed in 48 (48%, 26 men and 22 women) of the 102 (54 men and 48 women) patients diagnosed with mild influenza A virus subtype H1N1 at the First Hospital, Jilin University, China in 2009. Each patient was diagnosed by a physician according to the inclusion criteria of Influenza A Virus Subtype H1N1 Diagnosis and Treatment Protocol (Edition 3, 2009), issued by China’s Ministry of Health [2]. To ensure patients were not examined during or shortly after airway infections, all participants answered a questionnaire detailing any complaints of dyspnea, tiredness, cough, expectoration, medical treatment and smoking habits. The Modified Medical Research Council Dyspnea Scale was used to evaluate dyspnea of patients with abnormal pulmonary function (a score of 4 points, 2 cases; 3 points, 4 cases; 2 points, 14 cases;1 point, 4 cases; and 0 points, 2 cases) and with normal pulmonary function (a score of 4 points, 2 cases; 3 points, 2 cases; 2 points, 8 cases;1 point, 10 cases; and 0 points, 2 cases). Of these 48 patients, 38 were diagnosed by members of the Department of Respiratory Medicine and ten were diagnosed by members of the Department of Infection. The study included 26 male and 22 female patients with an average age of 29.5 years (range 27–39.5). Of the original 102 patients, eight (7.8%) had died: one from pneumonia and seven from disorders that could not be attributed to pulmonary disease. Fortysix (45.1%) patients were not re-examined due to practical problems. However, based on the data from 2009, these 46 patients did not differ from the 48 re-examined patients with respect to age, sex, disease duration, or degree of pulmonary function. Patients with chronic respiratory system disease (i.e. chronic obstructive pulmonary disease, asthma, pulmonary fibrosis, silicosis), chronic heart disease, or nervous and mental diseases were excluded. Written informed consent was obtained from each subject. Ethics statement The experimental protocol was established, according to the ethical guidelines of the Helsinki Declaration and was approved by the Human Ethics Committee of Jilin University, China. Written informed consent was obtained from individual participants. PLOS ONE | DOI:10.1371/journal.pone.0133698 July 28, 2015 2/6 H1N1 Virus Influences with Respiratory Systems Pulmonary function tests Approximately one year (±1 months) after recovery from influenza and discharge from the hospital, each patient included in the study was assessed for pulmonary function using the MasterScreen PFT system (Jaeger, Germany). The indices for pulmonary function as part of this test include: Tidal volume (VT), vital capacity (VC), flow-volume loop, forced expiratory volume at 1 second (FEV1), maximal mid-expiratory flow (MMEF), forced expiratory flow at 50% and 75% (FEF50, FEF75) and maximum voluntary ventilation (MVV). The indices for pulmonary diffusion function include diffusing capacity of the lungs for carbon monoxide (DLCO) and diffusion rate. Patients rested for 30 minutes before testing, and tests were performed in duplicate for each (...truncated)