Transfer to new places is usually in the personal items of the human they feed upon. Dwellings can become infested with bed bugs in a variety of ways, such as:

Bugs and eggs inadvertently brought in from other infested dwellings on a visiting persons clothing or luggage;
Infested items (such as furniture especially beds or couches, clothing, or backpacks) brought into a home or business;
Proximity of infested dwellings or items, if easy routes are available for travel, e.g. through ducts or false ceilings;
Wild animals (such as bats or birds) that may also harbour bed bugs or related species such as the bat bug;
People visiting an infested area (e.g. dwelling, means of transport, entertainment venue, or lodging) and carrying the bugs to another area on their clothing, luggage, or bodies. Bedbugs are increasingly found in air travel.Though bed bugs will opportunistically feed on pets, they do not live or travel on the skin of their hosts, and pets are not believed to be a factor in their spread. Diagnosis
A definitive diagnosis of health effects due to bed bugs requires a search for and finding of the insect in the sleeping environment as symptoms are not sufficiently specific. It is difficult to distinguish bed bug bites from other arthropod bites and the linear pattern of bites (known colloquially as "breakfast, lunch and dinner" bites) is not specific for bed bugs. If the number in a house is large a pungent sweet odour may be described. There are specially trained dogs that can detect this smell.
Bed bugs are insects from the genus Cimex that feed on blood, usually at night. Their bites can result in a number of health impacts including skin rashes, psychological effects, and allergic symptoms. Bed bug bites may lead to skin changes ranging from small areas of redness to prominent blisters. Symptoms may take between minutes to days to appear and itchiness is generally present. Some individuals may feel tired or have a fever. Typically, uncovered areas of the body are affected. Their bites are not known to transmit any infectious disease. Complications may rarely include areas of dead skin or vasculitis.Bed bug bites are caused primarily by two species of insects: Cimex lectularius (the common bed bug) and Cimex hemipterus, found primarily in the tropics. Their size ranges between 1 and 7 mm. They spread by crawling between nearby locations or by being carried within personal items. Infestation is rarely due to a lack of hygiene but is more common in high-density areas. Diagnosis involves both finding the bugs and the occurrence of compatible symptoms. Bed bugs spend much of their time in dark, hidden locations like mattress seams, or cracks in a wall.Treatment is directed towards the symptoms. Eliminating bed bugs from the home is often difficult, partly because bed bugs can survive up to 70 days without feeding. Repeated treatments of a home may be required.