This manual has been developed to guide rapid risk assessment of acute public health risks from any type of hazard in response to requests from Member States of the World Health Organization (WHO). The manual is aimed primarily at national departments with health-protection responsibilities, National Focal Points (NFPs) for the International Heath Regulations (IHR) and WHO staff. It should also be useful to others who join multidisciplinary risk assessment teams, such as clinicians, field epidemiologists, veterinarians, chemists, food-safety specialists.