On February 17, 2019, a male patient aged 13 years with no underlying medical conditions was evaluated in an Idaho hospital emergency department for a 1-day history of fever (103°F [39.4°C]), dry cough, sore throat, headache, and weakness. A respiratory specimen was collected and tested positive for influenza A by rapid influenza diagnostic test (RIDT). The patient was treated with oseltamivir as an outpatient and recovered. As part of routine surveillance, a second specimen collected during the emergency department visit on February 17 was forwarded to the Idaho Bureau of Laboratories (IBL), where CDC’s influenza reverse transcription–polymerase chain reaction (RT-PCR) diagnostic panel detected both pandemic influenza A and H3, which suggested an influenza A(H3N2) variant virus of swine origin. The specimen was sent to CDC’s influenza diagnostic laboratory for confirmation, and the patient was interviewed.