The Shadow of Alpha — Charles L. Grant

Introducing Parric: an ordinary civil servant being ground up in a mill of paperwork, who is given a chance to work on an experimental government project -- to live secretly in a town entirely populated by androids -- whose very existence, if it were known, would disrupt society -- something the repressive society does not want.

But Parric is happy in his secret village, protected by a force-field from outsiders, in contact with only a few others in similar positions in other secret villages. Protected, until war breaks out and civilization outside calls in the horrifying Plaguewind. Then the experimental androids, affected by the plague in strange ways, become killers! Parric must escape his village, then trek across the desolated countryside, in danger from the surviving mobs of plague victims, to the control center of the secret android project, in an attempt to join other men in starting a new civilization.