Methods
Patients
The protocol of this cross-sectional study was approved by the
Infectious Diseases and Tropical Medicine Research Center of Isfahan
University of Medical Sciences (MUI), Isfahan, Iran. Data collection was
performed from all consecutive subjects admitted to the Department of
Infectious Diseases and Tropical Medicine, Al-Zahra Hospital, MUI,
Isfahan, Iran. Our investigation was conducted from September 2017 to
February 2018. The criteria for the diagnosis of influenza were based on
the U.S. Centers for Disease Control and Prevention (CDC) and included
fever (37.8°C or higher), cough, sore throat, runny or stuffy nose,
muscle or body aches, headache, tiredness, vomiting, diarrhea, etc. The
demographic characteristics of the patients were recorded in a special
form. Associated factors including vaccination, contact with birds,
recent travel, and contact with patients were also noted.
Virological examination
For virological examination, in all suspected patients, throat swabs
were tested for the presence of specific viral antigens for A-H1N1,
B-H1N1, and A-H3N2 by means of real-time reverse
transcriptase-polymerase chain reaction (RT-PCR). The respiratory
samples were sent to the Tehran National Influenza Center in a viral
transport medium (Virocult, Medical Wire & Equipment, UK), where the
real-time RT-PCR protocol was applied using reagents supplied by the
World Health Organization (WHO).
Imaging procedures
In the present study, the chest computerized tomography (CT) scan with
intravenous (IV) contrast was performed to examine the pulmonary
involvement of the three mentioned viral strains in patients with
influenza. In this procedure, 120 ml (350 mg/ml) of IV iohexol
(Omnipaque™; General Electric) was administered, with images being
obtained after a 90-s delay. Provided chest scans were assessed for the
presence or absence of patchy infiltration, interstitial infiltration,
pleural effusion with or without infiltration, and also the site of lung
involvement.
Serological and clinical
examination
The assessed clinical manifestations included fever, headache, digestive
involvement, myalgia, vocal hoarseness, calf pain, and tachycardia. Each
variable was investigated as a simple ‘yes or no’ for symptoms. We also
recorded the white blood cell (WBC), lymphocyte, neutrophil, platelet,
C-reactive protein (CRP), alanine transaminase (ALT), aspartate
transaminase (AST), alkaline phosphatase (ALP), blood urea nitrogen
(BUN), hemoglobin (Hb), uric acid, lactate dehydrogenase (LDH),
erythrocyte sedimentation rate (ESR), creatinine phosphokinase (CPK),
total bilirubin (Bil-T), and direct bilirubin (Bil-D) levels; each
variable was assessed as a numerical value.
Statistical analysis
Statistical analysis was performed using the SPSS statistical package
program, version 22.0 (SPSS, RRID:SCR_002865). The demographic data of
the patients were analyzed using the Chi-squared and Kruskal–Wallis
tests. The comparison between the clinical and serological features of
subjects with various types of influenza was made using the Chi-squared
test. Continuous variables were assessed by analysis of variance (ANOVA)
to identify differences between groups. Differences were evaluated
further using Scheffe’s posthoc test if the ANOVA indicated
significance. P-values less than 0.05 were accepted as meaningful
differences.