With their crops safely immersed in the cold salt water of January, Katama Bay oyster growers and Island shellfish biologists met Monday with state officials to talk about ways to guard against another bacteria outbreak like the one that forced a temporary shutdown of their business late last summer.

In early September, Katama Bay was closed for almost four weeks after two people reported being sickened by oysters that were traced to the bay. The cause was Vibrio parahaemolyticus (Vp), a bacterial pathogen commonly found in warmer waters.

“This is an emerging issue,” said Julian Cyr, director of policy and regulatory affairs for the state DPH. “We definitely saw a problem with vibrio in the commonwealth from the end of June through August.”

Spokesmen from the state Department of Public Health, Fish and Game and Division of Marine Fisheries gathered at the Katharine Cornell Theatre for nearly three hours Monday morning as part of a listening tour to discuss a 2014 Vp control plan. Shellfish growers, members of the Martha’s Vineyard Shellfish Group, shellfish constables and health agents attended.

Julian Cyr: "This is an emerging problem." — Ivy Ashe

Vp causes gastrointestinal illness. Severe disease is rare and occurs more commonly in people with weakened immune systems. Vibrio infections can also occur when an open wound is exposed to sea water. Two or more reported cases from people not in the same household is considered a vibrio outbreak.

Aquaculture is a growing industry on the Island; the largest concentration of oyster farms is in Edgartown with 12 farms on Katama Bay and more planned for Sengekontacket and Eel Pond.

Shellfish is the second most regulated food in Massachusetts (the first is milk).

And vibrio cases are on the rise. There were 13 reported cases in 2011, 27 in 2012 and 58 in 2013. The Centers for Disease Control estimates that for every case reported, 142 cases are not reported. A vibrio control plan begun last summer outlined regulations for handling oysters and for closures in the event of outbreaks.

Officials say cases could be increasing because of increased oyster consumption, increased Vp awareness and warmer temperatures and waters.

Much discussion Monday centered on the difficulty in determining the origin of foodborne illness. Hospitals, doctors and labs report cases of vibrio to the department of public health and local health departments, which then conduct interviews with the people who became ill. This is followed by a review of shellfish tags and shipping to determine the origin of the contamination. There are many of points at which the shellfish could be mishandled, Mr. Cyr said, including the grower, the wholesale dealer and the retail seller.

He said tracing a vibrio case back to an individual grower is like winning “the bad luck lottery.” Most people who become sick do not go to the hospital, he added.

Jeremy Scheffer (right) operates one of 12 oyster farms on Katama Bay. — Ivy Ashe

Division of Marine Fisheries shellfish program manager Michael Hickey said they are still finding out “how much we don’t know and how much we need to learn.” There are 29 different strains of vibrio identified on the East Coast alone, he said.

Vp regulations vary among states. New York includes quahaugs in its regulations. In Virginia oysters can only be harvested in the morning.

Vibrio control plans are governed by the Interstate Shellfish Sanitation Conference, which meets later this month with Vp on its agenda. Proposals being considered for the North Atlantic states in 2014 include icing oysters within one hour of harvest, using ice slurries to cool shell stock, a Vp control plan for quahaugs and a new tiered procedure for closing and reopening areas that would include customer warnings in advance of closures and recalls.

Mr. Cyr said after the ISSC meets at the end of January, a second round of public meetings and education and training sessions are planned.

There were concerns about how the illness is identified. State public health food protection program director Michael Moore said that on average, 22 days elapse between onset of illness and when the food protection program gets information.

“It sounds like it’s difficult to collect data,” said Nic Turner, a Katama Bay oyster farmer. “Since we don’t have baseline levels [of vibrio in the water] to look at, how can we reopen safely and a little more efficiently?” he said.

“What is the expectation?” asked Edgartown shellfish constable Paul Bagnall. “I don’t see a way forward to success . . . are we trying to drive the cases in Massachusetts to zero?”

Mr. Hickey said the ideal would be a risk-per-serving of one case of vibrio per 100,000 servings. Currently the FDA identifies one serving as 13 oysters.

“Right now the acceptable level is one case,” Mr. Moore said.

Mr. Cyr said the goal is to avoid closures like the one in September. “This closure was significant to your businesses, your families, your livelihoods — we really want to rely on you and work with you on how we can avoid Vibrio illness and avoid these closures in the future,” he said.