Kutcher celebrated his 30th birthday with a host of A-list stars at New York's Socialista club on Feb. 7.
But the New York City Health Department has warned that a barman worked three nights at the venue when he was infected with Hepatitis A--including Kutcher's 30th celebration.
Last year, a sick member of celebrity chef Wolfgang Puck's catering staff inadvertently exposed stars, including Drew Barrymore and Hugh Grant, to hepatitis at a party following the launch of their movie Music and Lyrics.
And last February, Beyonce Knowles and the supermodel stars of the 2007 Sports Illustrated Swimsuit Issue were urged to get health checks after attending another Puck party, which featured the same Hepatitis A carrier among the catering staff.
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