Cal. Health & Safety Code § 101380

The resolution or ordinance shall be adopted and a certified copy served on the clerk of the board of supervisors on or before the first day of March of any year, and the services of the county health officer in the city shall commence on the first day of July following service of notice. The services shall continue indefinitely until the governing body of the city terminates them by adoption of a resolution and ordinance and service of a certified copy on the clerk of the board of supervisors on or before the first day of March of any subsequent year. The services of the county health officer shall terminate on the first day of July following service of notice.