The clinical characteristics of the 18 patients in our study are summarized in Tables 1 and 2. All patients presented with high fever (> 38.0� C, median value and range; 38.5� C Among our study population, one patient presented with high fever, severe nocturnal cough, and blood tinged sputum, and the respiratory symptoms eventually progressed into acute respiratory distress syndrome (ARDS), which further led him to receive mechanical ventilation (case No. 12). A retrospective medical chart review revealed that this patient was a solider serving in a different unit from the majority of the other patients and had been in contact with a patient with pandemic H1N1 2009 influenza virus infection lying in a nearby bed in our hospital prior to symptom aggravation. The laboratory data of this patient showed leukocytopenia, thrombocytopenia, and an increased CK level. Other laboratory tests were within normal limits. He was initially treated with antibiotics such as macrolide and a 3rd generation cephalosporin under suspicion of bacterial pneumonia, which was never confirmed. However, his symptoms did not improve. phosphate and antibiotics, the patient's symptoms improved and was taken off mechanical ventilation five days after antiviral agent administration.