NEW YORK, New York --

Celebrities attending Ashton Kutcher’s 30th birthday party at New York City hot spot Socialista Bar may have been exposed to Hepatitis A, Access Hollywood has learned.

According to a statement released by the New York City Department of Health, a bartender at the club, who was carrying the virus, worked on the night of Ashton’s February 7 party.

As a result, any patrons who may have visited the club are “considered to be at risk” and are being urged to get a preventive shot.

According to paparazzi photos taken that night outside the club, celebrities in attendance included Demi Moore, Lucy Liu, Salma Hayek, Gwyneth Paltrow, Madonna, Rebecca Gayheart and Eric Dane.

Hepatitis A is a liver disease caused by a virus. According to the release from the health department, it can be “spread from person to person by putting something in the mouth (even though it might look clean) that has been contaminated with traces of fecal matter from an infected person.”

The health department noted that most people “recover within a few weeks with bed rest and by avoiding alcoholic beverages.”

The owners of Socialista Bar told the health department they believe that about 700-800 people may have visited the club during the bartender’s shifts on the nights of February 7, 8 and 11.

"We are asking these bar patrons to get this vaccination as a precautionary measure," said Dr. Sharon Balter, Medical Epidemiologist at the Health Department. "If people experience symptoms, they should see a doctor, but for most people bed rest and avoiding alcohol are all that is needed to recover. This incident serves as an important reminder to always wash [your] hands thoroughly and regularly to prevent the spread of disease."

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