Swine Flu: Symptoms & Signs

  • Medical Author:
    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

Medically Reviewed on 9/30/2015

Swine flu (swine influenza) is a respiratory disease caused by viruses (influenza viruses) that infect the respiratory tract of pigs, producing most of the same symptoms in pigs as human flu produces in people. In certain cases, people have developed the swine flu infection when they are closely associated with pigs, such as farmers or pork processors. Modern flu outbreaks that have occurred due to flu viruses that contain genes from swine and other types of flu viruses have been referred to as swine flu. Most recently, the 2009 H1N1 influenza outbreak was due to a virus that was a mix of swine, human, and avian influenza viruses. In 2011, a new swine flu virus was detected, H3N2 influenza.

Symptoms of swine flu are similar to those caused by any influenza virus and include fever, chills, body aches, headache, cough, and nasal secretions. The first symptoms usually appear about one to four days after infection, with an average of two days. The symptoms last about one to two weeks and can last longer in some cases.


Kasper, D.L., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.

Medically Reviewed by a Doctor on 9/30/2015

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