Menemsha Pond and Katama Bay reopened to oyster harvesting on Friday morning after being closed for a week to investigate several cases of gastrointestinal illness. 

The state Division of Marine Fisheries notified shellfishermen and town officials that, after testing, the two water bodies had met national shellfish sanitation guidelines. 

The pond and bay were closed to oyster harvesting on August 1 after five people tested positive for Campylobacter, an illness that causes diarrhea, vomiting, fever and stomach cramps for up to seven days. The illness is primarily contracted from consuming raw poultry, but can be transmitted from raw seafood or contaminated water. 

Aquinnah board of health agent Marina Lent said to her knowledge, no one else has contracted the illness.

The closure was precautionary in nature. State officials said all ill parties ate raw oysters from the pond and bay during the week of July 12, prompting testing of the oysters and water. 

The oyster meat and water samples were collected from multiple locations in the pond and bay. They were analyzed by the Division of Marine Fisheries lab in New Bedford for fecal coliform levels. 

A recall for oysters harvested before the closure in both Menemsha and Katama was deemed unnecessary by the state. 

The Centers for Disease Control estimates 1.5 million people in the United States get ill from campylobacter each year. For oysters in Massachusetts, campylobacter contamination is rare due to rigorous shellfish safety standards, water quality testing and modeling and shellfish sampling, state officials said.

Rob Morrison, the shellfish constable in Edgartown and Isaiah Scheffer, shellfish constable in Chilmark, said it’s difficult for oyster farmers to have harvesting halted during peak summer season. 

They stressed that there is routine water quality testing each year, and the pond and bay are consistently found to harbor some of the cleanest waters in the state. A lot of work is put into ensuring Island oysters are safe to eat, they said, and during precautionary closures, oyster farmers often get the short end of the stick.

“I would like oyster enthusiasts to know that they can enjoy Katama Bay oysters with confidence,” Mr. Morrison said. “Please support [your] local oyster farmers after what has been a difficult week.”