I dunno about “infinite” actually. In one of my more successful playthroughs, my evac shelter was in worm territory. They seemed to stop spawning a little while after the zombies did (dynamic spawn). I noticed because I liked to hunt them for leather.
Incidentally, a character with fleet footed and high bow proficiency won’t find them all that threatening, especially while wearing kevlar and with nearby pavement to hide on in case of emergency. They get right up to you, but die before they get an attack in since you’re practically guaranteed headshots at pointblank range.
Then there’s graboids… shudder