The Public Health Advisor, or "PHA" is a type of public health worker which was established in 1948 by the United States Public Health Service in the Venereal Disease Control Division. Today they are hired primarily by the U.S. Centers for Disease Control and Prevention (CDC) and serve in many public health programs. This type of worker is unique in public health, because they begin their service at the entry level of public health doing what is known as "field work" or "contact epidemiology" which refers to the interviewing and locating of people who have been exposed to an infectious disease so as to offer them treatment and to reduce the epidemic. Following their initial work experiences, PHAs are exposed to a variety of public health programs across the United States, learning to function at all levels of the public health system. During their time of service, PHAs are called upon to respond to public health or humanitarian crisis. This article will briefly describe the history of the Public Health Advisor and will mention a few notable contributions made over the course of their history with the Public Health Service and later with the Centers for Disease Control and Prevention.