Bedbugs Aren’t as Contagious as You Think

Health and medicine explained.
Oct. 6 2011 7:16 AM

The Brown Peril

How contagious are bedbugs, really?

Illustration by Robert Neubecker.

Illustration by Robert Neubecker.

In the months after the Civil War, the New York Times sent several writers to the South. Between covering horse theft in Richmond and pondering whether one could tell a “yank” from a “reb” based on physiognomy, the reporters grumbled about an odious feature of their hotels: bedbugs. One wrote that he had come “from frequent experience” to view bedbugs as a Southern institution no less entrenched than slavery. Another begged readers for the name of a decent North Carolina inn, complaining that the “natives” there allowed bedbugs “full sway” such that “they now rule the State during the hours usually devoted to slumber without opposition.” He said he had tried to adopt the local custom of thinking “them’s only chinch-bugs” but failed. “[A]nd now at 8 o’clock in the morning of the 13th day of March, 1866, I am seated at my table, having been driven out of bed four times already … writing to soothe my rage and drown the blasphemy which wells up from my heart on account of ‘them chinch-bugs.’”

Not to doubt the yank reporters, but it is not clear chinch conditions were really less blasphemous to the North; one 1865 article said it was common to see bedbugs “crawling about the clothing of lawyers” in D.C. courtrooms. In that era, housewives swapped extermination tips alongside pudding recipes in newspaper household columns. Everyone had bugs, and it was very embarrassing. In 1908, a doctor with the New York City Department of Health had the temerity to declare in the Times that bedbugs had sacked Gotham. He assured readers that “a short zoological excursion” through any apartment or hotel suite would yield evidence of the “brown peril.” He exhorted New Yorkers to admit they had bedbugs, and stop insisting that the insects on the guestroom sheets “of course had been brought in from outside.”

Blame the guests, blame the rebs, blame any other unfamiliar person or place. Amid the current outbreak, this fear of catching bedbugs from strangers has reached new heights. In August, Animal Planet ran a show called “Bedbug Apocalypse” that warned, “There’s really nowhere to hide" and interviewed a woman so addled by biting houseguests that she insisted on steam-cleaning her chairs before she would sit. One talking head said that if we don’t act fast, “pretty much you can be guaranteed that you are going to take bedbugs home with you.” It’s a contagious fear: According to common belief, bedbugs are “world-class hitchhikers”—they spread so readily that sufferers get treated like outcasts. But is it true? Is a case of bedbugs really that easy to catch?

Investigating the question entails a consideration of bedbug epidemiology. Public health experts often consider three key factors when estimating whether a plague will spread or die out: the rate at which people come into contact with the pathogen, the duration over which an infection remains contagious, and the inherent transmissibility of the bug. Multiply these three factors together, and you get a value, called R0 (the basic reproduction number), that tells you the average number of people who will be infected by any one case. If R0 is less than 1, the contagion peters out. If it is greater than 1, the infection can spread.

We already know that R0 for bedbugs is above 1, since the plague has been spreading. In the current epidemic, hotel infestations have been key sentinel cases. Budget inns in West London became early prey for Cimex lectularius in 1997. Four years later, in 2001, outbreaks in big-city U.S. hotels popular among international travelers hinted that the resurgence was global—and caused some to conclude the bugs came from abroad. Looking back at the equation above, hotels have a high “contact rate”—they welcome a lot of strangers into bed—so rooms there are at elevated risk of infection. Some of these early outbreaks tended to linger, boosting R0, because exterminators at that point had little bedbug experience and infestations were not always completely eliminated.

But what about the last factor—the natural infectiousness of the pathogen? If you stayed in a hotel that had bedbugs—if you curled up in one of its bug-infested beds—what would be your chances of bringing them home with you? That is to say, are bedbugs highly “contagious,” like chicken pox? Or are they harder to pass along, like poison ivy? If we knew exactly how transmissible bedbugs are, we’d have a better sense of whether the Bedbug Apocalypse is really nigh. More importantly, we’d know how wary to be of motel beds, movie theater seats, and hugs from bug-afflicted buddies.

Scientists have examined the medical consequences of bedbug bites and investigated their potential to spread disease. (There is no evidence they do, though bedbugs have been accused, over the years, of spreading everything from cholera to polio to bubonic plague.) Few have studied their infectiousness, however. Many of the bedbug stats we hear originate from data gathered before World War II—complete with tales of zombie bedbugs surviving for three or four years without food—or ominous press releases from the pest-control industry (dutifully transcribed by leading newspapers) warning of bedbugs on trains, bedbugs in taxis, bedbugs everywhere! The average media consumer might be excused for thinking bedbugs are as unstoppable as the contagions spawned in Hollywood’s gray matter. Fortunately, it’s not true.

Clive Boase, a British pest consultant who works with one of the U.K.’s largest hotel chains, says managers of busy properties often assume there’s no way they can avoid catching bedbugs. They may note with a wink that some of their guests come from other European countries or otherwise have questionable hygiene. If you move enough grubby strangers through a bedroom, they say, then one of them will surely infect it. So Boase ran a test: He selected several hotels with bad bedbug problems, assiduously eradicated the pests with insecticides, and then monitored the premises for 12 months to see how long it took for the bugs to be reintroduced. The plague never came back, not even after one property had served nearly 100,000 new customers. “I’m not disputing the fact that bedbugs are spread by people. … But I believe that the reinfestation rate is much lower than the pest-control industry would often have us believe,” he says.

Another data point comes from New York City’s Department of Education, which maintains a kind of bedbug surveillance over its schools: teachers and staff are required to report bug sightings to the city, even if they've seen just one lonely insect. During the 2010-11 year, there were 3,590 confirmed reports of bedbugs in the school system’s 1,200 buildings, which are used by a little over a million students daily. How many of these cases resulted in the establishment of a full-blown colony on school grounds? Only once did an infestation bloom—seven bedbugs were discovered making whoopee in the closet of a Queens high school last December. Gotham’s vaunted serum-suckers thus gained a foothold in only 0.03 percent of their known school forays. Even this low figure may be an overestimate. No doubt other trespassers went undetected, ending their days in a quiet corner crack, gasping for a sup of blood. (Although bedbug lore says they can go for years without feeding, in reality they may last only a month or two.)

The notion that it may be harder for bedbugs to bivouac in dwellings than we have often imagined is supported by preliminary research into bedbug population genetics presented at a recent pest conference in Brazil. North Carolina State University entomologist Ed Vargo has gathered bedbug specimens from dozens of sites up and down the East Coast and analyzed their DNA to trace the outbreak’s origins and spread. In the infested apartment buildings he studied, he found that all resident bedbugs were close kin, even across widely divergent floors. That suggests they all arose from a single pregnant female or a handful of her eggs following a one-time hitchhike onto the premises. If successful bedbug invasions were common, Vargo says, he should see more genetic diversity. “It’s not like these things are being introduced constantly … it seems like these introduction events are probably kind of rare,” says Vargo.

Naturally, a building’s function affects its risk. Schools are not ideal hotspots; bugs prefer their foodstuffs to be sleeping (the better to reduce bloodsucking risk). Cinemas do not seem to be havens: Richard Pollack of the Harvard School of Public Health says none of the specimens he has examined from movie theaters has turned out to be bedbugs. Bedbugs do best in dense, multi-unit housing complexes, where hiding places abound and infestations can linger like tuberculosis. This highlights a key epidemiological insight: Despite the common refrain that bedbugs do not discriminate between princes and paupers, the poor are most at risk. In New York City, adults in the poorest neighborhoods are more than three times as likely to report having bedbugs as those in better-off areas. The poor are at risk because they often can’t afford exterminators and may have unresponsive landlords—factors that increase the duration of infection. They also frequently rely on donated or second-hand furniture, increasing their chances of catching bugs in the first place. Bedbug infestations thus are not random; they are reliably produced by social and economic conditions. Virginia Tech pest specialist Dini Miller says she separates the world into two types of people: those who may get bedbugs but will get rid of them, and those who may get bedbugs and will have to learn to live with them.

Case in point: a low-income housing complex with 1,200 units in Richmond, Va. In December 2009, Miller learned from the former landlord that the complex was 90 percent infested. (The new owners won’t discuss bedbugs with her.) From an epidemiological standpoint, these neglected edifices serve as reservoirs of disease. In out-of-control infestations, bedbugs can literally crawl out the door of one apartment and into another. A sofa exiting this complex might harbor thousands of eggs. And as we have learned in other epidemics, the likelihood of transmission depends not just on contact between infected and susceptible individuals, but on viral load.

Since dose is key, the real threat is the movement of stuff, not people. The chance of catching bedbugs via person-to-person contact is minimal. Unlike bacterial contagions, there’s no need to worry about shaking hands with people with bugs. But how about hugging? The risk of catching bugs via reckless hugging is extremely low, experts insist. Many draw the line at leaving your coat on beds at parties, however. Yet Miller, for one, says she doesn’t bother with common precautions such as keeping one’s suitcase far from the bed in hotels. She regularly tramps through bedbuggy buildings and currently has 31 bags of bugs in her living room (she is testing fumigants), but has never caught an infestation. “Bedbugs are not the worst thing that's ever happened to anybody. The people who freak out are the ones who have, like, eight bedbugs,” she says.

The prevalence of bedbugs has clearly gone up in recent years, but the rate of freak-outs has been increasing even faster. It's essential to recognize that the "disease" is just not that easy to catch. Although the insects have made a comeback—R0 is up—they are hardly lurking in every bus stop and banquette, as folks in the bug-busting business might have us believe. (Richard Pollack points out that 90 percent of the “bedbugs” he is asked to examine turn out to be other kinds of insects—or even specks of lint.) If the brown peril does strike, victims should remain calm and enlist professional help. Recently the CDC reported on a rash of poisonings in which people got sick after nuking their infested homes with insecticide, and history shows these episodes of friendly fire to be the bug’s deadliest effect. In the 19th century, reports of accidental death from drinking bedbug poison, suicide by insecticide, and fatal fires during bug exterminations—such as the tragic case of a New Jersey jeweler’s wife who accidentally roasted her spouse and infant child while fighting bedbugs with benzene in 1893—were all too common.

This is not to suggest we are regressing, entomologically speaking, to the buggy Victorian era. In fact, there is some evidence that the current bug craze could be topping out: According to new data from New York City, landlord bedbug violations declined in 2011 for the first time since 2004. Experts view New York’s bedbug problem as relatively mature, since the city is often seen as the epicenter of the outbreak. If New York’s drop is real and sustained, it could represent the start of a broader decline in bedbug prevalence, a downgrading of their international hobgoblin status, and a welcome reduction in nocturnal blasphemy. The little devils are not worthy of our rage. After all, them’s only chinch-bugs.

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Dave Johns is a doctoral student in Sociomedical Sciences at Columbia University’s Mailman School of Public Health. Amy L. Fairchild is a historian and professor of Sociomedical Sciences at Columbia University’s Mailman School of Public Health.

David Merritt Johns is a doctoral student with the Center for the History and Ethics of Public Health at Columbia University’s Mailman School of Public Health.

Amy L. Fairchild is a historian and professor of Sociomedical Sciences at Columbia University’s Mailman School of Public Health.