For public health emergencies, risk communication includes the range of communication capacities required through the preparedness, response and recovery phases of a serious public health event to encourage informed decision making, positive behaviour change and the maintenance of trust. Risk communication used to be viewed primarily as the dissemination of information to the public about health risks and events, such as outbreaks of disease and instructions on how to change behaviour to mitigate those risks. Thinking on this has now evolved dramatically as social science evidence and new communication and media technologies and practices have evolved in the 21st century.