Swine influenza, also known as swine flu, is an infection caused by several strains of swine influenza viruses primarily affecting pigs and occasionally humans. It was first recognized in 1918 and has seen significant strain mutations, notably the H1N1 subtype, which led to the 2009 outbreak declared a public health emergency. Prevention strategies include personal hygiene, vaccination for at-risk workers, and awareness of symptoms to ensure timely diagnosis and treatment.