Bed bug infestations have resurged since the 1980s for reasons that are not clear, but contributing factors may be complacency, increased resistance, bans on pesticides, and increased international travel. 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 1 city in the United States with the worst bed bug infestation. 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.
As bed bugs grow they molt, shedding their skin five times before reaching maturity. A blood meal is needed between each successive molt. Adult females also must feed in order to lay eggs. Under favorable conditions (70-80°F), the bugs can mature fully in as little as a month, producing multiple generations per year. Cooler temperatures or limited access to blood prolong the development time.
It was stated in 2012 that no truly effective insecticides were available. Insecticides that have historically been found effective include pyrethroids, dichlorvos, and malathion. Resistance to pesticides has increased significantly over time, and harm to health from their use is of concern. The carbamate insecticide propoxur is highly toxic to bed bugs, but it has potential toxicity to children exposed to it, and the US Environmental Protection Agency has been reluctant to approve it for indoor use. Boric acid, occasionally applied as a safe indoor insecticide, is not effective against bed bugs because they do not groom.
In infestations with persistent, repeated exposures, bed bug bites may appear in crops. Also, since bed bug bites usually take three to six weeks to heal, as long as the infestation is still present, new bites may accumulate even as the older ones start to resolve. Thus, people may have various bite reactions in various stages of evolution at the same time.
Bed bugs are an increasing cause for litigation. Courts have, in some cases, exacted large punitive damage judgments on some hotels. Many of New York City's Upper East Side home owners have been afflicted, but they tend to be silent publicly in order not to ruin their property values and be seen as suffering a blight typically associated with the lower classes.
The size of bed bug bites varies with a number of different factors. Bed bugs inject an anti-coagulant along with their saliva when they pierce the skin to take a blood meal. This anti-coagulant is mostly responsible for how a person reacts to the bite and determines the size of the bug’s bite. Since people will have various sensitivities to the bed bug’s bite, the size of the bite will vary, as well. Another factor that influences the size of a bed bug reaction is the number of times a person is bitten. Bite reactions of people bitten many times are also variable, and their response may be either more or less intense as the number of bites increases.