Filmed on location in Hiroshima.
American military made virus wipes out the world, then after everyone is dead, automatic systems in the US nukes the planet. Story is of the last handful of people that have to deal with this mess. Has all the hallmarks of a good samurai story, but with a virus. And nukes. A little over the top in some places and lets just say Chuck Connors English accent isn't entirely convincing but pretty compelling none the less.
Virus 1980 on youtube. At least it was when I typed this.