A Michelin-rated chef who calls himself a culinary alchemist was baffled by science of another kind recently: an outbreak of illness whose origin remains a mystery.

Celebrity chef Heston Blumenthal’s London-area restaurant, The Fat Duck, was shuttered for more than two weeks this month after 400 patrons reported falling ill with vomiting and diarrhea. The eatery, located in the village of Bray 30 miles (50 kilometers) west of London, reopened Thursday, according to the Associated Press.

Britain’s Health Protection Agency still hasn’t identified the source of the outbreak and it may take a few more weeks to do so. But  norovirus, also known as Norwalk-like virus, is being mentioned as a possible culprit. “Norovirus is a strong possibility,” the moderator for ProMed, a listserve for infectious disease experts, wrote in a March 6 post. “The incubation period from dining to onset of symptoms, length of illness, and the presence or absence of fever are three observations that can help distinguish a specific cause here.”

There are about 76 million cases of food-borne illness annually in the U.S., and about half are caused by norovirus. It’s also the most common cause of gastroenteritis in the U.K., where there are an estimated 600,000 to 1 million norovirus cases a year, according to the National Health Service. It’s spread when people eat, drink or share food contaminated with the virus or touch tainted surfaces, according to the U.S. Centers for Disease Control (CDC). Generally it takes a day or two for the symptoms, including vomiting, diarrhea and stomach cramps, to show up.

In 2005, The Fat Duck was voted the best restaurant in the world by a panel of prominent food critics, and in 2004 the high-end Michelin Guide gave it three stars. Blumenthal has collaborated with a physicist and psychologist to improve food quality and the eating experience, and he’s also a proponent of “slow cooking” that some say reduces the production of fats that occur during high-temperature cooking. "Science is a tool like the food processor and the oven," he told Britain’s Independent newspaper in 2006.

Blumenthal refused comment to British media and the news services on the status of the illness investigation, but said in a statement that he was “overjoyed to be able to get back to business as normal.”

Image of The Fat Duck by nsgbrown via Flickr