PITTSBURGH (AP) - Bedbugs aren't just sleeping with you. They're sleeping with each other.

Researchers now say bedbugs are able to inbreed with close relatives and still produce healthy offspring. That means that if just a few bedbugs survive in a building after treatment, they repopulate quickly. It helps explain why they're so hard to eliminate.

The new research was presented Tuesday in Philadelphia at the annual meeting of the American Society of Tropical Medicine and Hygiene.

Bedbugs are wingless, reddish-brown insects that bite people and animals to draw blood for their meals. Though their bites can cause itching and welts, they are not known to spread disease.

Researchers also say they found many different strains of bedbugs throughout the East Coast, meaning they're coming into the country from lots of different places.