Background and clinical characteristics of study subjects.

*<p>Wheezing was defined as a continuous high pitched sound emitting from the chest during expiration on auscultation.</p>†<p>Pneumonia was diagnosed on the basis of infiltrative shadows on chest radiograph.</p>‡<p>Asthma includes active asthma and inactive asthma.</p>§<p>Other comorbidities include smoking , alcoholism, diabetis meritis, chronic heart diseases , obesity.</p>¶<p>SpO₂: oxygen saturation measured by pulse oximetry in room air.</p>∥<p>Pathogenic bacteria co-infection was detected by throat swabs and/or sputum.</p><p>Definition of abbreviations: WBC, white blood cell count; LDH, lactate dehydrogenase; ALP, alkaline phosphatase; AST, aspartate amino transferase; ALT, alanine aminotransferase; CRP, C-reactive protein; IgE, Immunoglobulin E.</p

Treatment and clinical time course of study subjects.

*<p>Wheezing was defined as a continuous high pitched sound emitting from the chest during expiration on auscultation.</p>†<p>Pneumonia was diagnosed on the basis of infiltrative shadows on chest radiograph.</p>‡<p>Antiviral medication was switched oseltamivir to zanamivire and vice versa.</p>§<p>The dose of corticosteroid was equivalent to methylprednisolone 1.0–1.5 mg/body weight (kg)/time, 2–4 times/day, in subjects under 15 years of age, and 40–80 mg/time, 2–4 times/day in those over 15 years of age.</p>¶<p>At least one medication of shortacting β2-agonist, longacting β2-agonist, inhaled isoproterenol, inhaled disodium cromoglycate, aminophylline, and leukotriene receptor antagonists.</p>∥<p>Oxygen was administered using a nasal cannula or face mask.</p>**<p>Antibiotics.</p

Clinical presentation of subjects with pneumonia according to systemic corticosteroid treatment.

<p>N = 58.</p>*<p>No-steroid and steroid group denote group of subjects who were not treated and treated with systematic corticosteroids.</p>†<p>Wheezing was defined as a continuous high pitched sound emitting from the chest during expiration on auscultation.</p>‡<p>Pathogenic bacteria co-infection was detected by throat swabs and/or sputum.</p>§<p>SpO₂: oxygen saturation measured by pulse oximetry in room air.</p>¶<p>The number of days from symptom onset to the initiation of administration of antiviral agent either oseltamivir or zanamivir.</p>∥<p>At least one medication of short-acting β2-agonist, long-acting β2-agonist, inhaled isoproterenol, inhaled disodium cromoglycate, aminophylline, and leukotriene receptor antagonists.</p>**<p>Oxygen was administered using a nasal cannula or face mask.</p>††<p>The time (hours) to alleviation of fever to less than 37°C after the administration of antiviral agents.</p><p>Definition of abbreviation: WBC, white blood cell count; LDH, lactate dehydrogenase; CRP, C-reactive protein.</p

Clinical factors for using systemic corticosteroids treatment among the study subjects by multiple logistic regression analysis.

<p>n = 89.</p>*<p>Wheezing was defined as a continuous high pitched sound emitting from the chest during expiration on auscultation.</p>†<p>Pneumonia was diagnosed on the basis of infiltrative shadows on chest radiograph.</p>‡<p>SpO₂: oxygen saturation measured by pulse oximetry in room air on admission.</p

Study population.

<p>A total of 104 patients were diagnosed with pandemic influenza A(H1N1)pdm09. Five patients (one of whom died) were admitted to the ICU and were excluded from the study. The remaining 99 patients were the study subjects. Among them, 89 subjects presented with respiratory disorders and 10 presented with symptoms other than respiratory disorders, including encephalopathy. The subjects with respiratory disorders were classified into the following four groups: upper respiratory tract infection (n = 22), wheezing illness (n = 9), pneumonia with wheezing (n = 30), and pneumonia without wheezing (n = 28). The total number of subjects with pneumonia was 58.</p

Systemic corticosteroids treatment in the relation0 to clinical time course assessed by Kaplan-Meier methods.

<p>Kaplan-Meier curves of the number of hours to fever alleviation (A) and hospitalization days (B) according to systemic corticosteroid treatment among subjects with viral pneumonia in steroid (n = 46) and non-steroid (n = 12) groups There were no significant differences between the groups in terms of either hours to fever alleviation (log rank test, p = 0.835) or hospitalization days (log rank test, p = 0.626).</p

Life environmental qualities of study subjects.

*<p>Pandemic period, between April 2009 and July 2010; Post-pandemic period, between August 2010 and the end of survey period.</p>†<p>Location was defined by the accessibility of public service which is also followed by the Social Gap Index.</p

Factors relating to delayed seeking of health care, using multivariate analysis.

*<p>House constructed of concrete, tinplate, and combination of concrete and tinplate.</p

Availability of information related to influenza A(H1N1)pdm09.

*<p>Pandemic period, between April 2009 and July 2010; Post-pandemic period, between August 2010 and the end of survey period.</p

Additional file 1: of Chronological, geographical, and seasonal trends of human cases of avian influenza A (H5N1) in Vietnam, 2003–2014: a spatial analysis

Geographical disease clustering of incidence and mortality of human H5N1 infection in Vietnam between 2007 and 2014. (JPG 113 kb