As summer travel picks up, the potential spread of bed bugs grows. Those cities most affected by the infestation were outlined in a report of the top bed bug-infested cities in the U.S. and Philadelphia tops this year’s list.

Terminix, the world's largest pest control company, annually ranks major cities based on the number of infestations confirmed by their staff. This year's rankings have Cincinnati coming in second and New York City — the most-infested city for the past two years — coming in third. Cleveland, Miami, Houston, Indianapolis and New Haven joined the top 15 this year.

The report warns that the national bed bug epidemic, which began a few years ago, will likely spread to more cities as pests hitch rides with unknowing summer travelers. To be on guard against the pests, travelers and custodial workers should regularly check hotel mattresses, headboards and box springs for bugs, bug exoskeletons and dark blood spots. To avoid spreading the parasites, encourage travelers to hang all their clothing — don't store any items in drawers or lay them out on the bed or furniture. Luggage should be kept on the luggage rack or as far away from the floor as possible.

To avoid spreading the bugs after a possible exposure, immediately vacuum all surfaces and wash linens in hot water. In facilties already known to be infested, it might be advisable to take even more defensive measures, such as covering mattresses and box springs with a bug-proof plastic cover.

If you think the facility has contracted bed bugs, better call an exterminator: bed bugs are notoriously difficult to get rid of on your own. TIME magazine recently reported that "bug bombs" or "foggers" have been proven to be ineffective in exterminating the insects and can even make an infestation worse.