A small city might explain how two cases were both noticed by similarity, if this was happening elsewhere it's possible the cases aren't being picked up for specific cause as the reality of autopsy and forensic study in the real world is that many cause of death examinations can be more cursorary and less CSI.

One case was third party purchase of bat guano, the other raw sourced from the subjects own attic.

Clearly this could occur anywhere that bats roost and|or bat shit is shovelled out and onsold.