Workers and customers who handle live or raw fish or seafood from Chinatown markets in Brooklyn, Queens and Manhattan could be exposed to a bacteria that causes swelling and bumps on their hands and arms.

But the fish is safe to eat, officials added.

The department said it has identified an outbreak of a rare infection that enters the skin through a cut or other injury.

Customers and workers are encouraged to wear gloves while preparing the fish, especially people with cuts or abrasions.

The bacteria causing the infection is called Mycobacterium marinum and can be treated with antibiotics. If the infection isn’t treated correctly, it can worsen over weeks and require surgery.

Thirty cases have already been identified, said Health Department spokesman Levi Fishman.

He said the fish affected come from markets in Chinatown in Manhattan, Flushing in Queens and Sunset Park in Brooklyn.

Fishmongers in Manhattan’s Chinatown said they are usually careful about how they handle their products, but they also are now telling customers to keep their hands off.

“When we clean the fish, we wear rubber gloves and we use plastic bags to take up the fish,” said Asta Mak, 26 who works in The Haisein Co. fish shop on Grand Street. “We don’t touch with our hands. We don’t let the customers touch the fish. They point at what they want and we take it up for them.”

Jacque Even, 40, a chef from the Lower East Side, cooks fish at work and buys it twice a week to make at home. He usually touches the fish before making his purchase.

“I check it out before I buy,” Even said. “I touch it to feel the quality and make sure it is clean. I open the gill to see if it’s fresh. I’m going to have to stop doing that and point at what I want.”