Using a straightforward systems approach, Turnock Public Health: What It Is and How It Works explores the inner workings of the complex, modern U.S. public health system—what it is, what it does, how it works, and why it is important. Divided into two parts, Part I of the text focuses on the key elements of public health practice in 21st Century America, while Part II offers case studies designed to emphasize what public health is and how it works in practice. Collectively, this text gives students an understanding of the key concepts underlying public health as a system and social enterprise while enabling them to practice their knowledge with real-life public health problems, programs, and initiatives. The Seventh Edition introduces the concept of “Public Health 3.0�, with its new set of recommendations for updated public health practice in the 21st century and forms a unifying thread through the first six chapters of the book. A new appendix addresses COVID-19.