Dr. Jonathan Fielding, director of the county's public health department, said authorities have not ruled out other bacteria or viruses as additional reasons those attending a fundraiser became sick following the event, the Los Angeles Times reported Tuesday.
Legionnaires' disease bacteria are usually found in moist climates, unlike that of Los Angeles, Fielding said.
The bacteria causes respiratory illnesses, such as fever, chills and coughing. Healthy people usually recover by taking antibiotics, but death can occur in 5 percent to 30 percent of cases, the Times reported.
People got sick after attending DomainFest Feb. 1-3, which concluded with a fundraiser at the Playboy mansion, the Times said.
DomainFest urged attendees to complete a confidential survey to help health officials with their investigation, the Times said.