This paper, a chapter in a book on Marine Disease Ecology, focuses on global disease outbreaks that have resulted in mass mortality events that have subsequently impacted marine communities. One of the four case studies in the paper is the Sea Star Wasting Disease (SSWD) event that impacted the west coast of the US and Canada beginning in 2013. Data collected by REEF surveyors in this region on several species of echinoderms have been the basis of multiple published studies on the impact of SSWD. These studies are referenced in the book chapter.