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Michael: When you were a kid, your parents might have told you not to let the bed bugs bite. And for a long time, they were so unheard-of that you might have asked your parents what a bed bug even was. But today, bed bugs are the fastest growing pest control emergency in the developed world. 1 in 5 Americans either has had bed bugs, or knows someone who has.

And the problem isn’t going away. It’s actually getting a lot worse. Known into the scientific world as Cimex lectularius, bed bugs are blood-feeding insects that are about the size of an apple seed once they’re fully grown. They survive on the blood of mammals and insects, but they prefer human blood. A colony of bed bugs can have thousands of individuals. And you can have them without even knowing it. So here’s what you need to know about bed bugs.

[1. They don’t only live in beds.] The name “bed bug” might make you think they only live in beds. But bed bugs will live just about anywhere they can hide. An adult bed bug is five millimeters long and as narrow as a piece of paper, and they can crawl up to thirty meters in a night to find a meal.

That means bed bugs will hide behind light switches on the wall, underneath peeling paint and wallpaper, or in the gap between the walls and the baseboards, or just about anywhere else. Bed bugs have even been found living inside of a prosthetic leg.

[2. Bed bugs have preyed on humans for at least 3,500 years. ]We’ve been dealing with bed bugs for a really long time. We know they infested ancient Rome. The Romans actually brewed them and drank them as a cure for snakebites, which I’m sure was delicious. We also know they were in ancient Egypt, because the Egyptians wrote about them. Probably complaining to their landlords.

In fact, archaeological evidence tells us that bed bugs have fed on humans for at least 3500 years, because fossilized bed bugs have been found at dig sites. But bed bugs may have been plaguing us for much longer than that, based on what’s in their mitochondrial DNA — that is, the DNA inside the powerhouse of the cell.

By comparing the mitochondrial markers in bedbug populations around the world, we’ve learned that they originated in caves in the Middle East, where they would have fed on bats. Now, bed bugs can’t fly, and they can’t jump. They can’t crawl very far, either. Thirty meters a night isn’t setting any land speed records. So it’s a lot more likely that we met them when we went into their caves, instead of them coming out of their caves after us. Which means the first humans that bed bugs ever chewed on were probably cave-dwellers.

[3. Bed bugs hate heat.] So, we’ve had them forever, and they can hide anywhere. How can we get rid of them? The simplest way to wipe out a bed bug infestation is heat.

Both eggs and adults will die in under ten minutes if exposed to temperatures above 46 degrees Celsius. You know how in old-timey movies, cheap beds, like in hotels and hospitals, had all those janky metal frames? Metal frames were popular because you could rub them in kerosene and light them on fire. That would definitely take care of any bed bugs living inside of them.

Another method that was used to clear bed bugs out of furniture was to pack the joints with gunpowder and explode them. Maybe don’t try that one, though. SciShow is officially telling you not to set your bed frame on fire. Please don’t burn down your house.

[4. Bed bugs can hibernate] Even though bed bugs hate heat, you can’t just wait for them to die on a hot summer’s day, for a couple of reasons. First of all, just because it’s 46 degrees outside, doesn’t mean it’s 46 degrees where the bed bugs are actually living. In the shade under your bed, or in the cool recesses inside your walls? It’s a lot more comfortable.

But more importantly, bed bugs are capable of something called diapause. Diapause for insects is kind of like hibernation for bears. It’s a deep sleep, where the bed bug shuts off most of its metabolic processes and survives on its energy stores until it either runs out of energy or wakes up. Bed bugs enter diapause when it starts to get too hot, or if temperatures drop below freezing, or if they can’t find food.

That’s why putting your bedding in trash bags to try and starve the bed bugs out doesn’t work. Thanks to diapause, bed bugs can survive over a year without a meal. But in the same way that a bear won’t go into hibernation if you just stick it in a big freezer for a few hours, bed bugs won’t enter diapause if it only gets hot over a short period of time. Diapause is a reaction to slower, environmental changes... like the onset of summer. Which is why setting a bed on fire kills them.

[5. Bed bugs were almost wiped out in the 1950s.] But heat isn’t the only way to kill a bed bug. The reason you grew up thinking that bed bugs were maybe not even a real thing, is because bed bugs were almost wiped out in the 1950s.

All because of an incredibly useful but also super terrible, toxic little chemical called DDT. DDT stands for dichloro-diphenyl-trichloro-ethane, and it was the first chemical pesticide to be put to widespread use. It was rolled out after World War II, and by the end of the 1950s, bed bug populations had been so reduced in the developed world that scientists mostly stopped studying them, because they literally couldn’t find any.

DDT is from a family of pesticides called pyrethroids, which are synthetic versions of a compound created by the chrysanthemum flower. Here’s how it works: most animals, insects and humans included, have pores in the membranes of our nerve cells that can be opened to let in sodium. When sodium enters a nerve cell, it triggers a nerve impulse.

Pyrethroids bind to those sodium pores, locking them into the open position. That allows sodium to flood the cells. So nerve impulses start to fire uncontrollably, eventually leading to paralysis and death.

Pyrethroids have a much bigger effect on insects than they do on larger animals like birds or mammals. Even better, pyrethroids can affect insects at all stages of their life cycle, including when they’re in the egg. One treatment of DDT was enough to completely wipe out a population of bed bugs. And they would stay wiped out for up to a year. But DDT was banned in the US in 1972, for a lot of reasons.

For one thing, females who are exposed to DDT before puberty are five times more likely to develop breast cancer. DDT has also been linked to male infertility, as well as miscarriage, nervous system and liver damage, and developmental disabilities in children. It may not kill humans the way it kills insects, but it sure isn’t good for us. So we should like, not bring DDT back, ever.

[6. They can still be killed... sort of.] Modern bed bug treatments can be effective. But they’re costly, and not as reliable as DDT was. There are other pyrethroids now, for example, that don’t have so many harmful side effects. We can try using those against bed bugs, but the bugs have evolved a near-complete immunity to them.

Bed bugs today are ten thousand times less vulnerable to pyrethroids than they were fifty years ago. It goes back to those sodium pores. They’re made up of about two thousand amino acids, and it turns out that if you change just a handful of those amino acids, the sodium pore can still do its job.

But the pyrethroids can’t bond to those new amino acids. That makes pyrethroids, DDT included, totally useless against bed bugs. They don’t have anything else that works anywhere near as well. Steam treatments are effective: hot steam will kill bed bugs and their eggs. But the steam needs to come in direct contact with the bugs to kill them, which can be tough if they’re, like, inside your mattress.

In that situation, bed bug-proof mattress covers are available. Essentially, you wrap your bed in airtight plastic, and starve the bugs out. But like I said earlier, that can take up to a year. So... I hope you like the sound of crinkling plastic while you sleep.

You can also seal the cracks and crevices where bed bugs like to hide. That will cut down on the number of locations where they can lay their eggs. And linens and furniture can be put in a freezer unit for a couple of weeks to freeze the bugs to death.

If you have a bed bug infestation, you may end up needing a professional exterminator to do ALL of those things... and maybe more than once. The cost can run into the thousands of dollars. Okay, so is there good news? Well, yes, kind of.

[7. Bed bugs don’t spread disease.] It’s weird, for a blood-feeding insect, but bed bugs don’t spread disease. Most sources of human blood-borne illness break down inside of bed bugs almost immediately. For example, HIV, the virus that causes AIDS, decomposes in the bed bug’s digestive system in under an hour. Since bed bugs only feed once every few days, there’s basically no danger of it getting passed on through bites.

There are a few diseases that can survive for longer. Hepatitis B, for example, remains in the bed bug’s digestive system for up to six weeks after feeding. But there is no evidence that the virus will actually pass into a new host.

Bed bugs seem to be very clean eaters. Disease-carrying blood-feeders like mosquitoes can make you sick because of the compounds they inject into your bloodstream when they feed, like anesthetic so you don’t feel the bite and anticoagulants so your blood keeps flowing while they feed.

Those substances are tainted with the blood of their other victims. Bed bugs also inject you with anesthetic and anticoagulants — but without the blood mixed in. Theoretically, it’s possible that bed bugs could transmit something — say, if you rolled over on a bed bug, it burst, and its blood got into an open sore. Gross, I know.

But there’s never been a case of that actually happening. Scientists can’t even make it happen in a lab. The one exception is Chagas disease, which they managed to spread to mice by putting bed bug feces directly into an open scrape. But, again, it’s never happened to a person. So, if you’re dealing with a bed bug infestation, or just want to know what to do if you ever are, contact your local pest control experts.

Just don’t look to the lessons of history, because old school ways of wiping out bed bugs were... bad. Probably our best hope is that science will come up with something new. Something as effective as DDT, but not as, you know, awful.

And hopefully they come up with it soon, because after talking about bed bugs for ten minutes, I feel like they are crawling all over me. Oh, and half of people don’t respond to bed bug bites at all. There’s no itching, and no mark. So even if they’re snacking on you every night, you might not even know it.

On that note, thanks for watching this episode of SciShow, brought to you by our patrons on Patreon. If you want to help support this show, just go to Patreon.com/SciShow. And don’t forget to go to YouTube.com/SciShow and subscribe!