The FDA said 25 people developed nausea, vomiting, diarrhea and other symptoms after eating raw Texas oysters at a food event in Maryland between Feb. 9-11.
Testing by the Maryland Department of Health and Mental Hygiene indicated they had contracted norovirus, the FDA said. The virus can cause flu-like symptoms including fever, headaches and fatigue that can linger for several days, health officials said.
The oyster beds in San Antonio Bay were shut down by the Texas Department of Health Services on Feb. 24 and remain closed while the FDA conducts an investigation.
Doug McBride, spokesman for the Texas Department of Health, said Saturday that if contamination occurred, it did not appear to be widespread. He said how or where the possible contamination was introduced is also unclear. The department has tested the bay's water and did not find any problems, McBride added.
McBride said the virus could have occurred anywhere along the oysters' route from their habitat to diners, including the bay, dock, boat, dealers and food handlers.
John Hammond, a spokesman for the Maryland DHMH, said the department would not reveal any further details about the event where people got sick, including its location, because the incubation period for norovirus is very short and there is no lingering public health risk.
In its warning issued late Friday, the FDA said two seafood distributors — Bayview Seafood of Seadrift, Texas, and Rose Bay Oyster Company of Swanquarter, N.C. — have issued voluntary recalls of oysters harvested from San Antonio Bay. The recalled oysters are marked with tags that read: "Gal 1, 2/2/07."
Telephone messages and e-mails left with the FDA were not immediately returned Saturday.
The FDA also encouraged consumers who ate oyster products served in restaurants after Feb. 1 and experienced any symptoms of norovirus to contact their health care provider and local health department.
Consumers seeking more information were asked to call the FDA's food safety hotline at (888) SAFEFOOD or visit the FDA's Web site, www.cfsan.fda.gov.
San Antonio Bay is about 60 miles northeast of Corpus Christi, Texas, on the Gulf Coast.