1:18 Migration is a zombie/other creature, scifi horror post apocalyptic audio drama, in the same vein as WA, the story begins with a lead characters journal. We're Alive and 1:18 Migration came out around the same time, although I think 1:18 Migration came out a year before WA. If you like We're Alive, this would be a great series for you, they recently announced plans to revamp the series for a third season. They slso have a few books based on the series available.
You can download the episodes for free from 19 Nocturne Boulevard, and from One Eighteen's blogspot page.