Swine flu or swine influenza is a disease common in swine, with normal flu-like symptoms, but caused by any strain of the swine influenza virus (SIV – virus endemic in pigs). Although rare in humans, individuals with greater exposure to swine could contract swine influenza if the swine are carrying the particular rare strain of the SIV that is capable of affecting humans. Even then, it is a rare occurrence for the strain to be able to pass from human to human. This could occur if the SIV is able to mutate into a form that can easily be transmitted among humans.
The swine flu outbreak of 2009 is believed to be caused by such a mutated strain of the SIV. The current outbreak is called swine flu only because one of the surface proteins of the tested virus is similar to the one which infects pigs. It is still unknown if this is currently infecting pigs though it's clearly spreading among people, leading the World Health Organization to raise the Phase 4 pandemic alert. This new strain responsible for the outbreak has been found to be a re-assortment of strains of the influenza A virus subtype H1N1. These strains are separately endemic in humans and in swine.
According to the Centers for Disease Control and Prevention (CDC), Tamiflu (oseltamivir) and Relenza (zanamivir) would help in treatment and prevention. Antiviral drugs, if started within two days of the manifestation of symptoms, succeed in reducing the severity of the symptoms, preventing further complications, and hastening cure. The most effective method of prevention is to wash hands frequently with soap or with a foam or alcohol-based gel hand wash that helps wipe away bacteria and viruses. Vaccines against the 2009 H1N1 strain outbreak are in the development stage and are expected to be ready by June 2009.