The Centers for Disease Control and Prevention ( CDC ) , a United States government agency , reports that the symptoms and transmission of the swine flu from human to human is much like seasonal flu . Because these symptoms are not specific to swine flu , a differential diagnosis of probable swine flu requires not only symptoms but also a high likelihood of swine flu due to the person 's recent history . For example , during the 2009 swine flu outbreak in the United States , CDC advised physicians to `` consider swine influenza infection in the differential diagnosis of patients with acute febrile respiratory illness who have either been in contact with persons with confirmed swine flu , or who were in one of the five U.S. states that have reported swine flu cases or in Mexico during the 7 days preceding their illness onset . ''