Bed bugs occur in all regions of the globe.[7] Rates of infestations are relatively common, following an increase since the 1990s.[3][4][6] The exact causes of this increase is unclear; with proposals including greater travel, more frequent exchange of second-hand furnishings, a greater focus on control of other pests, and increasing resistance to pesticides.[4] Bed bugs have been known human parasites for thousands of years.[2]
It often seems that bed bugs arise from nowhere. The bugs are efficient hitchhikers and are usually transported into dwellings on luggage, clothing, beds, furniture, and other items. This is a particular risk for hotels and apartments, where turnover of occupants is constant. Bed bugs are small and agile, escaping detection after crawling into suitcases, backpacks and belongings. Acquiring secondhand beds, couches and furniture is another way that the bugs are transported into buildings. Bed bugs also can be carried in on one’s clothing, shoes or wheelchair. Once bed bugs are introduced, they can crawl from room to room or floor to floor. They can also be transported throughout buildings on people and their belongings. 
Unlike those of other insects, bed bug bites may sometimes appear in tight lines of multiple, small, red marks where multiple bed bugs have fed along an exposed area. Bed bug bites can cause itchiness. Initially, a victim may detect a slight burning sensation. The burning area then develops red bumps, known as papules or wheals (rash). In extreme cases, bites may swell dramatically or turn into blister-like skin inflammations.
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