Katama Bay oyster farms reopened Wednesday after a one-week closure spurred by reported cases of Vibrio illness linked to the bay.

Edgartown shellfish constable Paul Bagnall said the oyster farms were reopened at dawn on Wednesday, one week after a precautionary closure was initiated. There were no further reported cases of Vibrio illness from Katama oysters, Mr. Bagnall said.

Vibrio guidelines mandate a closure when there are four or more illnesses tied to the oyster growing area in a 30-day period. The Katama Bay closure came after there were four illnesses reported in a 35-day period, Mr. Bagnall said last week, and the state decided on a precautionary closure for the 12 independent oyster farms operating on Katama Bay.

Vp is a bacterial pathogen that naturally occurs in warmer waters. It can cause gastrointestinal illness, often including abdominal cramping, nausea, vomiting, fever and chills. Severe disease is rare and occurs more commonly in people with weakened immune systems. When raw oysters with high levels of Vibrio are consumed, they can cause illness.

So far this year, Katama Bay has been the only oyster growing area closed in Massachusetts because of Vibrio. Last September Katama Bay and other Massachusetts oyster growing areas were also closed because of Vibrio.

Oyster samples have been sent to labs for further testing to gather more information about what’s going on in the bay, Mr. Bagnall said. Over the winter, he said, the shellfishermen will likely discuss taking more proactive measures, including potentially closing the oyster farms during warmer weather.

“I don’t know if we just drew the unlucky Vibrio lottery number this year or is there something different in Katama Bay than Duxbury,” Mr. Bagnall said, noting that Duxbury has far more oyster farms.