Exterminator company Orkin released its annual list on Wednesday.
The top five cities this year are the same as last year, with Chicago being at the top of the list once again.
New York follows L.A., with Washington, D.C. and San Francisco rounding out the top five.
Orkin says the pandemic closures of many restaurants led rats to scavenge in new areas this year, with some displaying more aggressive behavior than in the past.
The regions were ranked by the number of new rodent treatments performed between Sept. 15, 2020, to Sept. 15, 2021, in both residential and commercial areas.
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The increase of rodents became so prevalent that the Centers for Disease Control and Prevention issued Rodent Control guidance on ways to keep rats and mice out of homes and businesses.
"As people resume normal activities, food availability will rise," says Ben Hottel, an Orkin entomologist. "Rodents are experts at sniffing out food and shelter, and they're resilient in their ways to obtain both. After a year of depleted resources, residential properties offer the ideal habitat for rodents, and once they've settled in, they're capable of reproducing rapidly and in large quantities."
There are multiple health issues associated with rodents as their presence may contaminate food, spread diseases and cause structural damage.
To help residents avoid the potential health and safety risks associated with rodents, Orkin recommends the following tips to help prevent rats and mice in and around the home:
Keep food stored away.
Small crumbs and garbage are popular food sources, as are dry goods such as grains and cereals. These should be kept in sealed metal or glass containers to prevent contamination.
Clear out the clutter.
Cardboard objects prove attractive to rodents, as they tend to chew them up for use in their nests. Take advantage of your extra time at home to clean and organize crowded spaces around the house.
Do not let the landscaping run wild.
Tall grass with adequate harborages, such as woodpiles next to the house, can be ideal habitats for rodents.
Inspect both inside and outside your home.
Key things to look for are rodent droppings, burrows and rub marks along baseboards and walls. The more quickly rodents are detected, the better.
Look for possible entry points.
Pay attention to access opportunities outside your home and seal any cracks and holes. Install weather strips around entryways, especially under doors, to help block rodents from sneaking inside.