Ahhhh! Hepatitis!!! You definitely have it if you're a famous person (like Lucy Liu or Demi Moore or Kate Hudson or Bruce Willis) who went to Ashton Kutcher's birthday party at downtown (that's the cool part!) Manhattan clurrrb Socialista. A bartender, hilariously and appropriately named Leif, was recently diagnosed with a "raging" (as the medical professionals at the Post are calling it) case of Hepatitis A, a disease that promises symptoms like diarrhea and jaundice. Jaundice? In Ashton's beautiful, murky eyes? This is worse than AIDS and Spanish Flu COMBINED. Spanish AIDS! [P6]