The singer may have been exposed to the disease after attending a Sports Illustrated party in Hollywood on Valentine's Day (Feb 14, 2007).

The Los Angeles County Department of Health contacted guests yesterday (Feb 27, 2007) to tell them a catering worker had been diagnosed with acute hepatitis A.

Vaccinations have been recommended for guests who ate uncooked food at the party or 13 other events catered by Wolfgang Puck Catering from February 1-20.

Carl Schuster, president of Wolfgang Puck Catering, said: "While the risk of infection is low, we will continue to work with to bring a speedy resolution to this investigation."

"After the cook was placed on medical leave we immediately worked to take every precaution to further safeguard our patrons and other employees."

A representative for Beyonce confirmed they "were looking into it."

Other guests at risk include Leonardo DiCaprio's former lover model Bar Refaeli.

Hepatitis A can be transmitted in contaminated food or through the poor hygiene of an infected person.

Symptoms include nausea, mild fever, and aching muscles. In severe cases the disease can cause liver failure. Most patients recover fully after two months.

Beyonce recently revealed she was terrified about appearing in Sports Illustrated magazine's famous annual swimsuit issue.

She said: "The shoot took a lot of guts. I'm a really shy person. Everyday I play a character and I had to tap into that."