What is the fine-grained topic of the following text: To describe clinical aspects of pandemic (H1N1) 2009 virus-associated pneumonia in children, we studied 80 such children, including 17 (21%) with complications, who were admitted to 5 hospitals in Japan during August-November 2009 after a mean of 2.9 symptomatic days. Only return the topic.
Clinical aspects of H1N1 virus-associated pneumonia in children