Background: Influenza A virus infection can cause pandemic influenza worldwide. The outbreak of the H1N1 virus occurred in Indonesia in April 2009. A total of 1892 suspected cases of H1N1 were reported between April and the end of December 2009. From 1892 suspected cases, there were only 809 confirmed infected by the H1N1 virus. Since the virus is a new strain, we wanted to know how many cases …