That is always concerning.

People often think they are "safe" because they don't keep native wild caught snakes.

However..
at many expos that is exactly what is being offered and sold. I'm not sure if its the same disease, but I've heard there was a dangerous disease spread from wild caught water snakes. The snakes were sold through a expo as well as online, through one of those "all kinds of species" re-sellers.

There could be potential cross contamination from wild caught species to other species kept at the same facility.

Its always a good thing to be aware, and only buy from reputable sellers. Also, to ALWAYS always do strictest of quarantine, esp. when the snake comes from questionable or unknown sources, or has been through several owners/sellers.