Bed bugs are bed bad. People’s entire lives have been overturned by these (increasingly common) blood-sucking, itch-inducing pests. Thankfully, they’re not disease vectors, but I would rather not share my home with a roommate who wants to eat me, thank you very much. 
 
 Scientists have noticed an expansion in bed bug cases across the world, in no small part due to increased international travel. But one team wanted to know how the bed bugs managed to hitch a ride, and how to prevent the spread. It turns out that part of the answer lies with the dirty laundry inside your travel bag. 
 
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 “There are a lot of good studies out there focused on trying to understand how bed bugs are attracted to humans and how they get around apartment blocks, but no one has really talked about how they get into the house in the first place,” study author William Hentley from the University of Sheffield in the UK told Gizmodo. “Stopping people from bringing bed bugs home can be a big step in preventing them spreading throughout the world.” 
 
 Scientists already know that human odor attracts bed bugs, though not which chemicals in the odor specifically. But for the newest study, researchers prepared a mock bedroom with laundry bags containing clean and dirty clothes—in other words, there were no humans in the room. The critters were “twice as likely to aggregate on bags containing soiled clothes compared to bags containing clean clothes,” according to the paper published today in the journal Scientific Reports. Contrary to the researchers’ hypothesis, the amount of carbon dioxide in the room did not affect their results—the CO2 source would represent a human, since some bugs like mosquitos are specifically attracted to the carbon dioxide you exhale. 
 
 These results were enough to convince the researchers that bed bugs could travel throughout the world by hitching a ride in luggage containing dirty clothes. 
 
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 As a caveat, this was an experimental room and not real life, said both Hentley and Toby Fountain, an evolutionary biologist from the University of Uppsala in Sweden who was not involved in the study. But still, said Fountain, the authors “demonstrate a striking pattern that bags containing clothes with human odor were more frequently used as refuges than those without. This result emphases the importance of making sure luggage and other belongings are made as inaccessible to bed bugs as possible when staying in increased risk places, for example by making sure bags are fully closed and secured and kept away from the bed.” Hentley agreed with this advice. 
 
 So there you have it. When traveling to possibly bed bug-contaminated locations—like, say, that sketchy-seeming hotel—keep your luggage on metal racks (bed bugs don’t like crawling on metal, said Hentley) or put your whole suitcase in a plastic bag to avoid picking up the horrors that are bed bugs. 
 
 [Scientific Reports] ||||| In the absence of a human host, bed bugs were twice as likely to aggregate on bags containing soiled clothes compared to bags containing clean clothes. Contrary to our predictions, elevated CO 2 did not affect this result. We did not observe bed bugs aggregating on the side of the room with the CO 2 source, but instead found an increased likelihood of bed bugs leaving their refuge. Our data are most consistent with the notion that elevated CO 2 initiates host-seeking behaviour. This is similar to findings in Aedes aegypti and Anopheles gambiae where very small increases in CO 2 concentration stimulate host-seeking behaviour19, 20. The position of the CO 2 source in a closed room above and away from the bed bug release point means directional cues as to the source of CO 2 may have been difficult for bed bugs to discern and so it is not possible to conclude whether or not the lack of aggregation on that side of the room suggests a lack of attraction to CO 2 . Many commercial bed bug monitors use CO 2 in conjunction with thermal and/or chemical cues, and claim higher catch rates than monitors without CO 2 . Our results suggest that any increase in capture rate in such devices10, 21 might be caused by increased activity rather than, or in addition to, increased attractiveness. 
 
 The smallest bottle-neck through which a new bed bug population can pass, and therefore the most likely passive (i.e. long-range) dispersal phenotype, is a single mated adult female5. There is some experimental evidence for a female ‘disperser’: work using small arenas and shorter time scales found that females were more active than males22 and more likely to disperse from aggregations with a 1:1 sex ratio23. By contrast, our study showed there was no significant sex difference in the number of insects found on bags with, or without, human smell (Table 1a). Since dispersal from the refuge may be initiated by hunger, we would expect females (with their higher metabolic rate24) to start host-seeking before males and potentially to do so more often. However, over longer periods, such as that used in this study, males and females are both likely to experience hunger and disperse from the refuge. Our design does not enable us to resolve this issue. 
 
 Our results do show that bags containing soiled clothes were significantly more attractive to bed bugs than identical bags containing clean clothes. Human odour is a known cue for host-seeking bed bugs11, but until now studies have focussed on how these cues determine the attractiveness of a sleeping host. Our results show that bed bugs will move to, and aggregate on, soiled clothing in the absence of a host. Bed bugs can sense 104 different volatiles16 found in the odorant profile of human skin25. Many of these volatiles are likely to evaporate from ‘soiled’ clothes for some time after they have been worn, removed and/or stored. We propose that residual human odour on soiled clothes acts as an elicitor of host-seeking or host-seeking-like behaviours, and that cues such as heat9 or elevated CO 2 may facilitate the activation and sensitivity of such host-seeking behaviour. Consequently, soiled clothing left in an open suitcase, or left on the floor, of an infested room is likely to attract bed bugs. When packed into the suitcase, they will accompany their host back home. 
 
 Our results show that over a period of several days bed bugs are attracted to, and remain on, soiled clothing: this provides a biologically realistic mechanism that underpins passive, long-range dispersal in bed bugs. The advent of relatively frequent, short-stay holidays in locations long distances from the hosts’ residence will facilitate the proposed mechanism of dispersal. Careful management of holiday clothing may be an important strategy in the prevention of bringing home bed bugs. ||||| Bed bugs love your stinky laundry. Here’s how to keep them away 
 
 On the surface, bed bugs seem ill-equipped for world domination: They can’t fly, jump, or swim; they can survive only on blood; and the world’s foremost apex predators—humans—want them all dead. Yet the parasitic arthropods have recently undergone what scientists are calling a “rapid global expansion,” taking over new territories and growing in number and range. And according to a new study, their globetrotting is made possible in part by an unusual form of transportation: our stinky laundry. 
 
 “It’s a good study,” says Richard Cooper, an entomologist at Rutgers University in New Brunswick, New Jersey, who was not involved with the work. He says it makes sense that the bugs are attracted to human odors, even on clothing. 
 
 Though they aren’t known to transmit disease, bed bugs (Cimex lectularius) can leave behind itchy bites and cause allergic reactions. In the middle of the 20th century, the pests had been largely eradicated from large parts of the developed world, but bans on effective pesticides in the 1990s, along with cheap air travel, have allowed the bugs to come creeping back. 
 
 Unlike ticks or lice, the apple seed–sized bed bugs aren’t travelers: They don’t stay on their hosts for long, and they rarely leave the beds and couches where they feast. So how were they getting onto planes? 
 
 “To me, hitchhiking seemed like the best explanation,” says William Hentley, an entomologist at the University of Sheffield in the United Kingdom. “That then led me to this question of whether they’re attracted to our clothes and the smell of humans.” 
 
 To figure out whether the bugs were indeed stowing away in our laundry and luggage, Hentley and his colleagues tested whether the insects were attracted to soiled clothing. They set a cage full of bed bugs in the middle of a room and placed two cotton bags at equal distances—one filled with clean clothes and the other filled with dirty socks and T-shirts collected from volunteers. The researchers released the bed bugs from the cage and let them wander freely for 96 hours. 
 
 At the end of the experiment, about twice as many bugs were attracted to the dirty clothes as to clean ones, the team reports today in Scientific Reports . That jives with prior experiments that have shown that bed bugs can smell more than 100 compounds produced by human skin—many of which could easily linger on clothes for multiple days, the researchers say. 
 
 They also tested whether increases in carbon dioxide—long thought to signal a nearby meal—made the bugs more or less likely to go for the smelly clothes. When added to room, the gas seemed to trigger foraging behavior, but the bugs weren’t any more likely to go for the dirty clothes than they were initially. That suggests that carbon dioxide prompts the bugs to forage, but it doesn’t help them home in on the smelly laundry, the team concludes. 
 
 So what can you do to keep the six-legged parasites out of your suitcase when you travel? Hentley is careful to point out that he hasn’t studied these techniques scientifically, but he recommends simply putting your bags up on the metal luggage racks in a hotel room, because the bugs can’t climb up smooth surfaces. If no such rack is to be found, keeping your soiled garments in an airtight bag should help mask the smell. But bear in mind that if you’ve previously put dirty clothes in your luggage, you might need to wrap up your whole suitcase, he says. 
 
 Cooper agrees that plastic bags might work, but he doesn’t use them himself. “The biggest thing is not keeping your luggage on the bed,” he says. Another option: putting your bags into a portable heating chamber whenever you get home and washing and drying your clothes on high heat. “Heat is the Achilles heel of the bed bug,” Cooper says.
– Nobody wants to bring home bedbugs after being on the road, and now scientists have some practical advice on how to avoid that fate. A new study in Scientific Reports shows that the little critters are drawn to the scent of dirty laundry, and the lead author translates that into traveling tips. For starters, put your luggage up on metal racks in a hotel room because bedbugs won't be able to climb up the smooth surface, says entomologist William Hentley of the UK's University of Sheffield, per Gizmodo. You might also store your dirty clothes in a separate airtight bag. If the hotel has no metal racks, consider storing your entire suitcase in a plastic bag, which may seem like a pain, but nothing compared to the chore of ridding your home of bedbugs. "Soiled clothing left in an open suitcase, or left on the floor, of an infested room is more likely to attract bed bugs," the authors write. "When packed into a suitcase, they will accompany their host back home." They figured this out by unleashing bedbugs in a room and leaving them be for 96 hours. Roughly twice as many bugs ended up in a cotton bag filled with dirty laundry as opposed to a bag of clean clothes. A Rutgers entomologist who wasn't involved with the study tells Science it's legit and offers some advice of his own. "The biggest thing is not keeping your luggage on the bed," he says. Travelers also should wash and then dry clothes at the highest temperature upon returning home, he adds, because "heat is the Achilles heel of the bedbug." (Another study suggests the bugs prefer certain colors.)