Bed bugs are usually transported on personal belongings, moving from location to location passively. They may crawl into a suitcase, backpack or other item and be carried off to a new location. Often times (see Reproduction and Lifecycle) these hitchhikers will be pregnant females.
You may bring bed bugs into your home on your personal belongings or a visitor may unknowingly carry them in. A child returning home from college or a family member returning from a trip or stay at the hospital could bring them in. Bed bugs are not an indication of a dirty home, all they require is a ride in, a small crevice to hide in and a human to feed from.
A common way for bed bug infestations to spread by bringing home used furniture or clothing. It is recommended that you avoid buying or accepting used items or if you do inspecting them very carefully. Do not pick up furniture put out to the trash. It may have been discarded because of an infestation.
Bed bugs can also spread on their own, moving from room to room or apartment to apartment. They can easily travel through wiring and plumbing runs, along heating vents, through wall and ceiling voids, through elevator shafts and through laundry and mail chutes.
Bed bugs will actively migrate when: the room that they inhabit becomes vacant and they are seeking a new host; they are exposed to ineffective types or amounts of pesticides that repel them without killing them; or when the area they are in becomes too overpopulated.
Bed bugs spread more easily in places with high human traffic such as hotels, apartment buildings and schools than in single family homes.
Another, less common way for another type of bed bugs, called bat bugs, to be introducted into a new location is by being carried in by birds or bats.