TAMPA, Fla. (WFLA) – The Centers for Disease Control and Prevention is continuing to investigate a recent outbreak of norovirus linked to raw oysters harvested in Texas.

As of Thursday, 211 total norovirus cases linked to the raw oysters have been reported in Alabama, Florida, Georgia, Louisiana, Mississippi, North Carolina, Tennessee and Texas, according to an updated CDC outbreak advisory. The agency also acknowledged that there are likely more than 211 cases, as some of those sickened may not report or seek treatment for their illnesses.

Officials said the outbreak appears to stem from oysters from harvest area TX 1 in Galveston Bay, Texas.

The affected oysters were harvested between Nov. 17 and Dec. 7, and were sold at retail and restaurant locations across the aforementioned eight states, though it’s possible they may have been distributed to other states as well, the CDC said.

On Dec. 9, Publix issued a recall after Texas health officials reported over 40 illnesses. The chain said the oysters, which had a Global Trade Item Number (GTIN) of 29697000000, were sold at both Publix locations and Publix GreenWise markets.

The FDA later confirmed that the oysters were potentially contaminated with norovirus.

“Norovirus is the leading cause of foodborne illness in the United States,” the CDC said. “However, state, local, and territorial health departments are not required to report individual cases of norovirus illness to a national surveillance system. That’s why we may not know about many cases, especially if people do not go to a doctor’s office or hospital.”

According to the CDC, there are about 2,500 norovirus outbreaks each year in the United States, mostly concentrated between November and April. Norovirus symptoms can include diarrhea, vomiting, nausea, and stomach pain. These symptoms can start within 12 to 48 hours of exposure to the virus.

Those who are older or pregnant, and those with compromised immune systems, are at greater risk of illness. Anyone who is suffering from illness symptoms such as fever, nausea, diarrhea, vomiting, abdominal cramps, chills and headache should seek medical attention.

Infected individuals are also at risk of dehydration, health officials warn.

Anyone who believes they may have purchased a package of contaminated oysters from Galveston Bay is being instructed to discard them. Those who purchased unpackaged oysters are encouraged to contact the seller to learn where they were harvested.

Additional guidance for retailers, restaurants and consumers is available at the CDC’s website.