Cal. Health and Safety Code § 120290 states: any person afflicted with any contagious, infectious, or communicable disease who willfully exposes him/herself to another person is guilty of a misdemeanor.
In theory, you could file a police report and seek to have charges brought. It may also give rise to a civil lawsuit.
Disclaimer: This answer is provided as a public service and as a general response to a general question, it is not meant, and should not be relied upon as specific legal advice, nor does it create an attorney-client relationship.