@doncentman if you mean the creatures that attacked Scarlett and the ones at the basement? They’re one, not different. If you can recall, in the earliest chapters of the story, some patients at the Sinclair facility morgue were infected by the serum, killing a couple of workers at the facility as a result of that.
Thomas knew the serum was responsible for transforming the deceased patients to zombie, so he decided to create them on a larger scale hence the hundreds of newer ones at the basement. The few that were created at the facility morgue escaped in the earlier chapters and they’re responsible for the death of Luke and his makeout girlfriend, the girl at the Grenville cinemas and now Scarlett’s attack.
So in a nutshell, they’re all one group of creatures, created at different times. I hope I’ve been able to answer your question? Thanks for reading.
@doncentman Yes it is. There is only one hole in Grenville but Rose and June never fell into the hole, they only trailed Dominic to the hole site and the fumes made them collapse. They never got inside like Thomas did.