Statistical analysis
Data were analyzed with SPSS Statistics 19 (SPSS, Inc., USA).
Distribution normality was checked for all variables including age and
gender. The comparison of the age was
analyzed by Mann-Whitney U test. Due to the unequal group sizes and the
data variance, Chi-square test or Fisher‘s exact test was used to
analyze the association between age, gender and year groups with
respiratory viruses. A P value of <0.05 was considered
statistically significant.