Watch Free Online HD Moviesjoy. A man-made virus, 'The Killing Strain'-- an out-of-control swine flu-- turns infected humans into raging monsters. As it rapidly spreads, a group of uninfected survivors must make life-or-death decisions before the U.S. military firebombs the area in a desperate attempt contain the contagion. The survivors are unaware that the virus has already reached their group-- by infecting one of them-- and now the merciless metamorphic process has begun.