Theories abound on the origins of this highly contagious and adaptable virus: it may be the creation of an ancient Sith Lord; a naturally occurring result of the industrial toxins released into Taris's oceans; or the spectacularly failed efforts of medical researchers to artificially engineer a broad-spectrum vaccine.
Whatever the origins, the effects are undeniably terrifying. Typically spread through direct contact with rakghouls, fortunate victims suffer acute onset of flu-like symptoms that can prove fatal if not properly treated. However, in roughly half the cases the disease causes the host to undergo a horrific mutation, actually transforming them into a rakghoul.
Virtually all humanoid species in the galaxy are susceptible to infection, and there are rumors that the Empire has undertaken efforts to weaponize the disease. Unsubstantiated reports of rakghouls on worlds other than Taris lend credence to this rumor… or indicate the disease is slowly spreading across the galaxy of its own accord.