The purpose of this document is to clearly describe the proposed research questions and methodology for a systematic review on water, sanitation, and hygiene (WASH) interventions in disease outbreaks. The systematic review has a singular overarching objective in assessing the impact of emergency hygiene interventions. The primary research question will be answered through four secondary objectives that further evaluate: a) use of service and disease reduction; b) positive intervention characteristics; c) cost-effectiveness; and d) non-health related factors of emergency WASH interventions in disease outbreaks. This review is funded through the Humanitarian Evidence Programme, a UK Aid-funded partnership between Oxfam and Feinstein International Center (FIC) at the Friedman School of Nutrition at Tufts University. The Humanitarian Evidence Programme aims to synthesize evidence in the humanitarian sector and communicate the findings to stakeholders, with the ultimate goal of improving humanitarian policy and practice.