I doubt that they are fleas. Maybe colembella or a mite of some sort. Ivermectin will treat mites. I also found that hot shot pest strips kill all crawling and flying insects in your home including mites. They have warning labels about not being used in areas used for more than 4 hours a day but they work and haven't bothered me or my pets or husband for months. Check areas that are damp.
i found a nest in my shower shelf.