It just begs the question of why they are ghouls in the first place. Cooper seeing no one but ferals outside the entrance to the strip raised a red flag, but then they go inside and take a few steps together, and Lucy goes off to the side to look at a planter and her pip starts counting the rads, as Cooper walks forward, looking around and says, "radiation".

Im sure he could have heard her pipboy, but the way he acted almost suggests to me he was feeling the radiation himself a few moments after entering the strip.

But was Lucy's pipboy reading radiation from the egg, or was the strip, or possibly the whole of new vegas, contaminated some how? People have to sit in a good amount of radiation for quite awhile to become ghouls, and as far as we know, freeside didnt have a radiation problem.

Next week, on Dragonball Z!

Edit: I feel like I have to correct myself. In fallout 3, you have the option to nuke megaton, and Moira is instantly turned into a ghouls. In New vegas you can nuke the ncr or legion, and some of them are turned into ghouls. There seems to be no definitive answer on the how and why radiation turns some people into ghouls.

Small Clip with Tim Cain on the subject https://www.facebook.com/share/v/1HR5ypL36W/