Steadily-rising resistance to DDT and other potent pesticides may have also contributed; bans on DDT may have contributed as well, though studies have shown resistance continued to rise in countries where they continued to be used.The U.S. National Pest Management Association reported a 71% increase in bed bug calls between 2000 and 2005. The number of reported incidents in New York City alone rose from 500 in 2004 to 10,000 in 2009. In 2013, Chicago was listed as the number one city in the United States for bedbug infestations. As a result, the Chicago City Council passed a bed bug control ordinance to limit their spread. Additionally, bed bugs are reaching places in which they never established before, such as southern South America.The rise in infestations has been hard to track because bed bugs are not an easily identifiable problem and is one that people prefer not to discuss. Most of the reports are collected from pest-control companies, local authorities, and hotel chains. Therefore, the problem may be more severe than is currently believed. Species
The common bed bug (Cimex lectularius) is the species best adapted to human environments but is also known from birds, Chiroptera, Gallus (chickens and relatives), Myotis myotis, and sheep (Ovis aries). It is found in temperate climates throughout the world. Other species include C. hemipterus, found in tropical regions,  which also infests poultry (including Gallus)  and bats, and Leptocimex boueti, a relative of C. lectularius adapted for the tropics of West Africa and South America, which infests bats and humans.
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.