Investigating an outbreak of acute fever in Chuuk, Federated States of Micronesia.

Objective: In September 2012, there was an unexpected increase of acute febrile illness (AFI) in Chuuk State of the Federated States of Micronesia. At the same time, dengue outbreaks were occurring in two of the Federated States of Micronesia's other three states. The cause of AFI was suspected to be dengue; however, by the end of October, only one of 39 samples was positive for dengue.