A national search has been launched for a new medical director of the Louisville Metro Department of Public Health and Wellness.The post was vacated late last month when Dr. Matt Zahn accepted a job in California.Zahn, a California native, is the new epidemiology medical director at the County of Orange Health Care Agency.He had held the Louisville post since 2004, and served as acting health department director after Dr. Adewale Troutman took a job in Florida last year.Louisville Metro Board of Health Chairman Bill Altman says Zahn did outstanding work in Louisville."We’re very sorry to see Dr. Zahn go but we recognize this is a big opportunity for him."Zahn sought to succeed Troutman permanently, but the job went to Dr. Laquandra Nesbitt, who has led the department since mid-summer.