[Study on clinical symptoms and influencing factors of influenza-associated severe acute respiratory illness in children younger than 5 years old in Suzhou of China, 2011-2017].

To study the influencing factors of influenza-associated severe acute respiratory illness (SARI) in children younger than 5 years of old in Suzhou, and to provide evidence to support the improvement of prevention and control strategies for influenza in children. We conducted a prospective influenza surveillance for hospitalized SARI and outpatient influenza-like illness (ILI) at Children's Hospital of Soochow University from April 2011 to March 2017. We compared the clinical and other characteristics of influenza-positive patients with SARI to those with ILI to find the differences and to identify influencing factors of influenza-associated SARI, using test and unconditional logistic regression. We found 786 cases of influenza-associated ILI and 413 cases of influenza-associated SARI during the study period. Cough, runny nose, shortness of breath, asthma or wheezing were more common in influenza-associated SARI than in influenza-associated ILI (<0.01). Univariate and multivariate logistic regression showed that the influencing factors which significantly associated with increased risk of influenza-associated SARI were as follows: younger age (<6 months 3.6, 6-23 months a=2.5), respiratory infection history within 3 months (a=4.5), chronic lung disease history (=3.4), fever above 39.0 ℃ (39.0-39.9 ℃ a=2.4, ≥40.0 ℃ a=6.0), and the presence of A/H1N1 (a=2.3), A/H3N2 (a=1.9). Children younger than 2 years old, with a history of chronic lung disease, a history of respiratory infection within 3 months, or with a fever peak above 39.0 ℃ should seek medical advice as soon as possible or receive annual influenza vaccination to reduce the incidence of influenza-associated serious outcomes.