The health department sent an e-mail Friday to all attendees warning them that they had received a cluster of reports that people had become ill after attending the conference and the Playboy Mansion event. The e-mail asked recipients to fill out a survey. The reports of illness complained of respiratory problems, including pneumonia.

The Feb. 3 event at the Westwood mansion was part of the annual DOMAINfest Global conference. This year’s gathering was held the first week of February at the Fairmount Miramar Hotel in Santa Monica.

Hugh Hefner's legendary Playboy Mansion is the focus of a Los Angeles County Department of Public Health investigation after reports that dozens of visitors contracted a mysterious respiratory illness after attending a fund-raiser there earlier this month.

David Castello, 54, who co-founded Castello Cities Internet Network Inc. with his brother Mike, said he and his brother were among those who attended the conference and visited the mansion fundraiser. Castello said he became ill a day after the event. “It knocked me off my feet for five days,” Castello said. “I’m over it now, but I’m still feeling fatigue, which is not a good thing.”

For the last few days Castello said he had been recovering from a fever, a dry cough, headaches and back spasms. He said his brother, who was mostly outside on the night of the event, did not get sick. Attendees of the fund-raisers have logged onto Facebook to report their illnesses. Many suspect their symptoms are related to Legionellosis, or Pontiac fever— a milder form of Legionnaires’ disease, which is caused by bacteria living in warm air-conditioning systems.

Many of those who became ill said they suspect a fog machine that was used at the party.

Roughly 700 people attended the conference from 30 countries, according to organizers. “It’s the perfect storm to spread this,” Castello said.

Domainfest has not responded to an e-mail request for comment by The Times. A Playboy rep told the New York Post that the Playboy Mansion has been contacted by the health department and is cooperating fully with the investigation.

-- Ruben Vives

Photo: Playboy Mansion. Credit: L.A. Times