New York City hot spot Socialista is sending out a warning to patrons, including celebs who attended Ashton Kutcher's birthday there on February 7th.

Evidently a bartender has contracted Hepatitis requiring everyone who has been at the bar during the times that the employee was working to be on alert.

"In response to a case of Hepatitis A in a bartender at Socialista in Manhattan, the Health Department today notified patrons of the exposure and urged them to get a hepatitis A vaccination as a precautionary measure," the Health Department statement reads. "Hepatitis A is spread by putting something in one's mouth (even though it might look clean) that has been contaminated with traces of fecal matter from an infected person. Any patron who visited the establishment after 8 p.m. on February 7th or 8th, or after 10 p.m. on February 11th (the times the infected person worked after becoming infectious), is considered to be at risk and needs a preventive shot. "

Ashton's birthday guest list included Kate Hudson, Madonna, Bruce Willis, Lucy Liu, Liv Tyler, Roberto Cavalli, Eric Dane and his wife Rebecca Gayheart.

Hepatitis A is a virus that is spread from person to person, usually by putting something in the mouth that has been contaminated with traces of fecal matter from an infected person.

Symptoms include jaundice, or yellowing of the eyes and skin, fatigue, and abdominal sickness. Most people recover within a few weeks.