Hepatitis A is the most common cause of viral hepatitis in the world and it’s very possible that the bartender who reportedly served Ashton Kutcher and his friends drinks at a Manhattan hotspot transmitted his infection to the A-list celebrities, said Dr. Manny Alvarez, managing editor of health for FOXNews.com.

Hollywood is under a hepatitis alert after a bartender at Socialista tested positive for hepatitis A. New York City officials are urging people who visited the club on Feb. 7, 8 and 11 to get a hepatitis A vaccination as a precautionary measure.

Among the people who reportedly attended Socialista on those dates are A-listers like Kutcher, his wife Demi Moore, Madonna and Kate Hudson.

Alvarez said the bartender could have passed along the infection to patrons through his contact with food, water and ice. He said club attendees should be vaccinated within two weeks of exposure.

“The highest risk of infection is within two weeks of transmission,” Alvarez said.

Alvarez said hepatitis A is not as problematic as hepatitis B or C, which can be chronic conditions, and that hepatitis A usually clears itself up within six weeks. However, hepatitis A can be harmful for people with pre-existing health and liver problems.

“You could get it and have no symptoms,” Alvarez added. “So people should get the immunization post-exposure to be on the safe side.”