The 2009 flu outbreak in humans, known as "swine influenza" or H1N1 influenza A, refers to influenza A due to a new H1N1 strain called swine-origin influenza virus A (S-OIV). The new swine flu virus is actually a genetic mixture of two strains, both found in swine, of unknown origin. S-OIV can be transmitted from human to human and causes the normal symptoms of influenza. Prevention of swine influenza spread among humans includes use of standard infection control measures against influenza and constitutes the main scope of World Health Organization. For the treatment of S-OIV influenza oseltamivir and zanamivir are effective in most cases. Prophylaxis against this new flu strain is expected through a new vaccine, which is not available yet. Worldwide extension of S-OIV is a strong signal that a pandemic is imminent and indicates that response actions against S-OIV must be aggressive.