The county's Department of Public Health issued a statement Saturday saying only that it was investigating a suspected respiratory infection outbreak among attendees of a conference on the west side of Los Angeles County.
The Los Angeles Times said there were reports that dozens of people were sickened after the event at the L.A. mansion, but neither the newspaper nor county health officials cited a specific number of cases.
The department sent an e-mail with a survey Friday to all who attended the Feb. 3 event, saying that they had received reports of problems including pneumonia, the newspaper said after talking to participants.
Some 700 people from 30 countries attended the Santa Monica conference on Internet businesses, called Domainfest global.
The county statement said investigators were looking into the cause, extent and potential sources of the illness, but did not believe it spread beyond the people who attended.
"Public Health has no information suggesting that this suspected outbreak extends beyond those individuals associated with this conference," the statement said.
Officials from the department would give no further details on the investigation.
Elliot J. Silver of New York, who runs Silver Internet Ventures, succumbed to the bug.
"It is scary everyone came down with the same thing at the same time," Silver told the New York Post.
David Castello, 54, said he and his brother, Mike, who co-founded Castello Cities Internet Network, Inc., were also at the fundraiser. David Castello fell prey to the infection, his brother did not.
"It knocked me off my feet for five days," said Castello, whose symptoms included a fever, cough, headaches and back spasms. "I'm over it now, but I'm still feeling fatigue, which is not a good thing."
Representatives from Playboy and the conference did not immediately reply to requests for comment.