PORTLAND  — A strain of a drug-resistant skin disease that has afflicted sports teams, prisons and military units is now proving a persistent pest among lobstermen and their families on a Maine island.

Over the past two summers, more than 30 people on Vinalhaven have come down with painful and persistent skin infections that required repeated treatments with intravenous antibiotics for some of the victims — but medical authorities say lobster lovers need not worry.

There’s no indication that the germ is linked to lobsters, and boiling or steaming them would kill any bacteria that infected fishermen who handle them might leave behind, said Dr. Stephen Sears, Maine state epidemiologist.

The working theory is that methicillin-resistant staphylococcus aureus, also known as MRSA, moves easily among lobstermen because their work — hauling traps, cutting bait, handling lobsters — causes plenty of scraped knuckles, pinched fingers, and small cuts and nicks, giving MRSA a foothold, Sears said.

“They really do have a lot of small traumas to their hands,” Sears said. “That’s just the nature of dealing with the ocean, the traps, the lobsters, the bait fish, a variety of things.”

No deaths have been associated with the outbreak, but lobstermen and others have sought treatment at the island medical center. Some have been treated multiple times.

Landon Morton, a lobster fisherman, has battled staph infections four or five times in the past year and a half since first coming down with MRSA while working on one of the town’s docks. Just a few weeks ago, he began his latest bout — and his 18-month-old daughter has it, as well.

Morton said there’s no mistaking it for a run-of-the-mill skin rash, because it’s painful.

“It starts with a little red sore,” he said. “Within a couple of hours it swells and turns really red. The first time I had it, about half of my leg was swollen and red. It’s nasty.”

Hospitals have been dealing with infections caused by the “superbug” for 30 years, said Nicole Coffin of the Centers for Disease Control and Prevention in Atlanta. Community-acquired MRSA, the strain that’s making the rounds in Vinalhaven, tends just to cause skin lesions, Coffin said. Left untreated, however, they, too, can become deadly.

Previous instances of community-acquired MRSA have involved prisons, military recruits and sports teams, Coffin said. Perhaps the best-known case involved the St. Louis Rams in 2003, when the CDC was called in to investigate a cluster caused by skin abrasions and locker room contamination.

MRSA is carried on human skin and can be transferred to others through towels, gloves or other shared items. But it’s a bit of a medical mystery how MRSA arrived on the 1,200-resident island in Penobscot Bay.

Some islanders believe it started with workers on one of the wharves. Some wonder whether the staph is in the water. Others wonder whether it somehow originated with the herring bait used by lobstermen.

All of those scenarios — and the chance of pinning down the culprit — seem unlikely. MRSA is not carried by seafood, so that rules out herring bait and the lobsters themselves, Sears said. And while MRSA has been documented in sea water and on beaches, it doesn’t survive in those environments in concentrations necessary to cause human infection, he said.

To cut down on MRSA infections, people dealing with the infections on Vinalhaven are following guidelines recommended by the CDC: frequent hand-washing, use of disinfectants, washing clothes in hot water and setting the dryer on hot.

Morton said he always had good hygiene. But these days he takes multiple showers daily, washes his hands frequently and even changes clothes several times a day. He keeps disinfectant wipes close at hand.

“Some people will call it a little bit of a phobia, but it’s to the point where I’m careful about everything I touch,” Morton said. “I’m very paranoid about keeping things clean.”