Bed bugs are pretty much everywhere. They’re being spotted in major cities like Paris, London and even Toronto now. They’ve been found in 135 countries in the world, according to a recent study, and they can live in mattresses, couches, walls, lightswitches, even books. For a while, we were doing well at keeping the bed bugs in check, but not anymore.Murray Isman, a professor and dean emeritus at UBC’s Faculty of Land and Food Systems, explains how bed bugs became so prevalent, and why they’re so good at sticking around.Questions? Comments? Ideas? Email us at thedecibel@globeandmail.com