Washington, D.C., has been ranked the top bed bug city in the country – surpassing nearby Baltimore in the process – by pest control company Orkin.

Baltimore was ranked No. 1 for three straight years before falling to No. 2 on Orkin's annual list this year, according to a Monday news release from the company . Washington was ranked No. 2 last year.

Chelle Hartzer, an Orkin staff entomologist, tells U.S. News that Washington and Baltimore were "probably pretty close last year." Possible reasons for the two cities consistently being ranked so high are their size and the amount of domestic and international travel in and out of them, she said.

"The more people you have, the more prevalent these pests can be," Hartzer adds.

A bed bugs-focused information page on Washington's Department of Health website notes that the insects were extinct decades ago, but that an increase in global travel and the discontinued use of "caustic" insecticides due to healthy-living initiatives have allowed the pests to have a resurgence.

"Now, our nation is much more habitable for the bed bugs," according to the webpage.

The office of Washington Mayor Muriel Bowser did not respond to a request for comment from U.S. News.

Orkin bases its list on data from the 50 metro areas where it performed the most best bug treatments from Dec. 1, 2018 to Nov. 30, 2019. Rounding out the top 10 were Chicago; Los Angeles; Columbus, Ohio; New York; Detroit; Cincinnati; Indianapolis and Atlanta.

"While bed bugs have not been found to transmit any diseases to humans, they can be an elusive threat to households," Hartzer said in a written statement . "They are excellent hitchhikers, and they reproduce quickly which make it nearly impossible to prevent bed bugs. Sanitation has nothing to do with where you'll find them."

In its news release, Orkin warned that signs of bed bugs could include "small black spots indicating bed bug feces or nymph bed bugs in places such as mattress seams, bed frames and furniture." The company recommended that people inspect their homes regularly, decrease clutter, examine secondhand furniture and frequently wash bed linens with hot water.