The appearance of a flea in an apartment full of pets is cause for alarm, but the appearance of a flea in one with no pets can be baffling. That is, it can baffle anyone except pest control techs. Fleas don't suddenly appear out of nowhere, so there is a reason that you've just found one even though the apartment complex you manage doesn't allow pets. Keep in mind that fleas can breed quickly, so you need to alert your pest control company now and start routinely treating the complex until the problem is gone.
Who Just Moved?
Fleas, believe it or not, typically don't like humans. They like cats and dogs and the occasional other furry animal, but they don't infest human-only spaces unless the fleas are really starved. So it is possible for humans to get flea bites, but it is also possible for humans to eventually get rid of the flea problem.
That being said, someone who just moved in might have brought stray fleas with them from their old place. A new tenant who moved in and who had pets before, in their old home, could have brought in some fleas or flea eggs unwittingly. You should also make sure that no new tenants are trying to sneak around the no-pet rule and creating little flea farms of their own, and it's possible someone like that just moved out, leaving a lot of the bugs behind
Who Just Visited?
Chances are that even in a no-pet complex, someone has had a pet visit, and that pet may have brought in the fleas. Chances also are that you have not seen every visiting pet, so if you know of a couple that have stopped by but didn't think they were the cause, they might not have been. It is nice, if you know of people who bring by service dogs, for example, to notify the service dog owners of the problem so that the owners can be sure the service dogs' flea control is up to date.
It's not unusual for a flea to jump onto someone's clothing as they're walking around, and then that person brings the flea home. So that flea could have been a one-time deal. However, if the flea was about to lay eggs and ended up doing that in someone's carpet, then you have a problem. Over-the-counter carpet treatments can help, but if you still have a problem, call in a pest control company like Anteater Pest Control. And then arrange for bimonthly pest control services to ensure that the problem remains gone.
You can have an apartment complex that is relatively free of pests. Nature is nature, and you can't prevent every bug from getting inside, but regular pest control services help prevent intrusion. If you don't already have a contract, start looking now. A simple perimeter spray and inspection every couple of months can make a big difference.