Four of the cases involved men who have sex with other men, including three who were HIV positive, the department said. The county is subsequently urging vaccinations for some gay men, particularly those with multiple partners of who share drug paraphernalia or cigarettes.
Three men have died, two of whom were HIV positive, the County Health Department said in a news release.
Meningococcal disease can be spread through kissing and coughing or sharing beverages or cigarettes. The infection can cause brain damage, hearing loss or potentially death.
Three of the patients were known to socialize in the West Hollywood and North Hollywood areas, according to the department.
Free vaccinations will be offered to people without health insurance by the department beginning Thursday.
The Associated Press contributed to this report.