In late April 2009, a swine-origin novel influenza A/H1N1 virus was identified among humans in Mexico and the United States. It was made known that novel H1N1 virus was antigenically and genetically unrelated to human seasonal influenza viruses and genetically related to swine influenza viruses. Since then, It has rapidly spread to every continent, and WHO promptly declared the virus as the the first influenza pandemic of 21st century on June 11, 2009. As of July 9, 2009 a total of 94,512 confirmed cases including 429 deaths were reported worldwide. Children and young adults were more commonly infected with novel influenza A/H1N1 virus with the a small percentage of elderly population. Most cases of influenza A/H1N1 infection were uncomplicated, characterized by influenza-like symptoms and spontaneous recovery. Some cases resulted in gastrointestinal symptoms including diarrhea and vomiting. About 3~9% of patients with confirmed cases have been hospitalized, and some of them have had previous medical conditions such as asthma, cardiovascular disease, diabetes, immunosuppressive therapy, pregnancy and morbid obesity. Case fatality rates vary from 1.2% to less than 0.1% while relatively higher in developing countries. This review describes the current epidemiology, clinical manifestations, treatment, infection control and prospects of the 2009 influenza A/H1N1 pandemic.