Mr. Wong said many of his clients were being cited for rat infestations, though, conversely, violations are not going up citywide: the number of violations for rodents issued since Hurricane Sandy dropped to 1,996, compared to 2,750 for the same period the previous year. Still, the figures offer an incomplete picture. After Hurricane Sandy, as of Nov. 1, the Health Department said it stopped issuing violations for rodents in Zone A, which includes parts of all five boroughs, among them Battery Park City in Manhattan; Red Hook, Coney Island and parts of Dumbo and Brooklyn Heights in Brooklyn; City Island in the Bronx; and the Rockaways in Queens.

Jim O’Brien, the owner of Pest Quest Pest Management on Staten Island, said rat problems had been especially acute in wetland areas and shorelines on Staten Island and in New Jersey. There, many homes are empty and being repaired by workers, who leave behind pizza boxes and uneaten food. “It’s really an open playing field for the rodents,” he said. Still, he gave credit to New York City’s Sanitation Department for working around the clock to clear storm debris. “They put a damper on what potentially could have been a serious issue,” he said.

One rainy night this week, Manuel Medina, an exterminator for M&M, amassed an array of rat-killing devices: giant glue boards, poison and serrated devices called T-Rexes that snap shut like bear traps. He headed to a nasty basement in Chinatown — “kind of like a Freddy Krueger basement,” he said, one so nasty that some of his fellow exterminators had refused to venture in.

The basement was pitch black, its ceiling lined with tangled, dusty cables and sagging, cobwebbed pipes, its floor strewn with belly-up cockroaches, its walls mottled with water bugs. A distant pipe dripped steadily. In short, it was rat heaven.

For people like Ms. Heming, rats have always been a part of life in New York, but she says the problem has grown since the storm. Mr. Medina is not sure whether the hurricane is to blame, but he said the city’s rat problem was getting worse, with more construction on the go, and more garbage being poorly stored, as trash bags split open, dripping juices and grease.

He made his way quietly around the Chinatown basement, led only by the dim glow of his smartphone, until he found what he was looking for: three freshly dug rat holes, and droppings that might have been left by a small dog.

Mr. Medina reached into his bag and pulled out several blocks of poison. “For the big boys,” he said, but he knew he would be returning. “It’s been an ongoing battle,” he said, “We kill ’em, but they’ll still keep coming.”