# Introduction and background
During public health emergencies, people need to know what health risks they face and what actions they can take to protect their lives and health. Accurate information provided early, and in languages and channels that people understand, trust and use, enables them to make choices and take actions to protect themselves, their families and communities from the health hazards threatening their lives and well-being.
Risk communication is the real-time exchange of information, advice and opinions between experts, community leaders, officials and the people who are at risk and is an integral part of any emergency response. In epidemics and pandemics, in humanitarian crises and natural disasters, effective risk communication allows people at risk to understand and adopt protective behaviours. It allows authorities and experts to listen to and address people's concerns and needs so that the advice they provide is relevant, trusted and acceptable. Although risk communication is an intervention used in all areas of public health, this guidance has specifically been developed to provide the most up-to-date evidence-based recommendations for communicating risk in health emergencies. For the purposes of this guidance, emergency risk communication (ERC) is an intervention performed before (as part of preparedness activities), during and after (to support recovery) an emergency to enable everyone at risk to take informed decisions to protect themselves, their families and communities against threats to their survival, health and well-being.
While there are many guidelines on communications in general and risk communication in particular, this is the first to be based on a systematic analysis of the evidence on what has and what has not worked during recent major outbreaks and emergencies, such as the West African Ebola virus disease outbreak in 2014-15 and the global Zika virus outbreak in 2015-2016. Systematic reviews of the quantitative and qualitative evidence were performed and the quality of the evidence analysed using a range of validated tools. To ensure no evidence of recent experience was missed, a rapid review covering the most recent grey literature was also performed.
The recommendations in these guidelines provide a framework of the elements of effective ERC. They do not aim to provide step-by-step guides to the practice of risk communication. These will be developed as derivative products such as implementation guides, checklists, field manuals and training courses.
The recommendations in these guidelines provide a framework of the elements of effective ERC Why these guidelines were developed 2. Why these guidelines were developed WHO has manuals, training modules and other forms of emergency and risk communication guidance based on expert opinion or lessons drawn from major environmental disasters, such as the SARS outbreak of 2003, and the H1N1 influenza pandemic of 2009, rather than on systematic analyses of the evidence.
Recent public health emergencies, such as the Ebola virus disease outbreak in West Africa in 2014-2015, emergence of Zika virus syndrome in 2015-2016, and multi-country yellow fever outbreaks in Africa in 2016, have highlighted major challenges and gaps in how risk is communicated during epidemics and other health emergencies. Major challenges include the changing role of traditional media (newspapers, radio and television) and the rapid transformation in communication technology, including near-universal penetration of mobile telephones and the widespread use, and increasingly powerful influence, of digital media. Important gaps include considerations of context: the social, economic, political and cultural factors influencing people's perception of risk and risk mitigation behaviours. There is a need for guidance on the best approaches for strengthening ERC capacity and sustaining that capacity for any health emergency.
In January 2015, the WHO Executive Board convened a special session to recommend actions to better manage the ongoing West African Ebola virus disease outbreak and passed a resolution recognizing the urgent need for countries to build strong, resilient and integrated health systems capable of fully implementing the IHR ( 2005) (1). The resolution explicitly "requests the Director-General to continue to develop and implement an Organization-wide communications strategy to improve routine communications, messaging about preventive measures, risk communication, and emergency communications, ensuring that the new policy entails matching the content, form and style of communication with the media, timing and frequency that will reach the intended audience and serve its intended purpose..." (4).
Signatories to the IHR (2005) have requested WHO support for building and sustaining their risk communication capacities. These capacities include: engagement of risk communication partners and stakeholders; an up-to-date risk communication plan that has been implemented and tested during an actual emergency or simulation exercise; policies, standard operating procedures, and guidelines covering clearance and release of information during a public health emergency; regularly updated information sources accessible to the media and the public for information dissemination; accessible and relevant information, education and communication materials tailored to the needs of the population; and the use of evaluation to inform risk communication planning.

# Recent public health emergencies  have highlighted major challenges and gaps in how risk is communicated during epidemics and other health emergencies
Communicating risk in public health emergencies: a WHO guideline for risk communication (ERC) policy and practice Objectives and scope of the guidelines 3.

# Objectives and scope of the guidelines
Who should use these guidelines?
These guidelines were developed for policy-and decision-makers responsible for managing emergencies, particularly the public health aspects of emergencies, and practitioners responsible for risk communication before, during and after health emergencies.
Other groups expected to use these guidelines are: frontline responders; local, national and international development partners; civil society; the private sector; and all organizations, private and public, involved in emergency preparedness and response.
Existing relevant guidelines 5.

# Existing relevant guidelines
WHO and its partners have developed several forms of guidance on risk communication over the last two decades (Table 1). 6.

# How these guidelines were developed (methodology)
Scoping the guidelines Development of these guidelines began in October 2014, with the establishment of an Internal Steering Group (ISG) and the commissioning of a flash literature review (2) (full report available at this link to provide an overview of existing ERC guidance and potential areas for action or improvement. The flash review found a number of areas where guidance was lacking, including: mobile technologies; evaluation research; assessment of barriers to preparedness; ERC during disasters in very low-income countries (LICs); capacity building during the preparedness phase; and the application of evidence and past experience for better ERC. A Guideline Development Group (GDG) of experts in risk communication, disaster preparedness and response, and health emergencies, was established in early 2015 (see Annex 1 for full list of names, expertise and affiliations). The GDG held a first meeting in Geneva, Switzerland, on 22-23 June 2015, to use the findings of the flash literature review to set the scope of the guidelines, identify areas of risk communication practice needing further investigation, and frame questions to govern a systematic search of the evidence. Communicating risk in public health emergencies: a WHO guideline for risk communication (ERC) policy and practice How these guidelines were developed (methodology)
The following 12 questions were framed and used to guide evidence reviews (Table 2).

# Searching and analysing the evidence
The search questions were further developed into the Setting, Perspective, phenomenon of Interest, Comparison, Evaluation of impact (SPICE) format by Jane Noyes, the guideline methodologist supporting the GDG, along with the guideline secretariat and the GDG chair. The SPICE format was chosen over the more commonly used Population Intervention, Comparison, Outcome (PICO) format because SPICE is considered more applicable to a qualitative and mixed-methods evidence search, and it was expected that this type of evidence would be predominant. Q9. Community engagement: What are the best ways to engage communities in emergency risk communication activities to respond to events/contexts? Q10. Social media: What are the best social media channels and practices to promote health protection measures and dispel rumours and misinformation during events and emergencies with public health implications? Q11. Communicating uncertainty: What are the best ways to communicate uncertainties to public audiences, at-risk communities and stakeholders? Q12. Messaging: What elements and timing of messages are best at influencing public/community levels of concern to motivate relevant actions to protect health? How these guidelines were developed (methodology)
The SPICE questions were used to provide search terms for the systematic reviews commissioned in 2016 and completed by the end of January 2017 (see Annex 3 for full SPICE question terms). All systematic review reports are available at this link. Full details of search methods and quality assessment evidence are available in Annex 2. There were four different methodological streams in the evidence synthesis:
quantitative with comparison groups 2.
quantitative where descriptive survey methods were used 3.
qualitative methods 4.
mixed-method and case studies.
The reviewers synthesized the findings from studies placed in each methodological stream and then rated the confidence in/certainty of the findings (giving a rating of 'very low', 'low', 'moderate' or 'high') using the tools below. The methods used by systematic review groups to develop the evidence synthesis are summarized in Figure 1 below.  Communicating risk in public health emergencies: a WHO guideline for risk communication (ERC) policy and practice How these guidelines were developed (methodology)
While the systematic reviews were underway, the West African Ebola virus disease outbreak, the emergence of Zika virus syndrome and other major public health emergencies generated considerable grey literature on risk communication. To capture this, a rapid grey literature evidence search was undertaken that examined the reports relevant to the 12 questions in Table 2 that ended on 31 December 2016.

# Evidence for recommendations
When all the systematic reviews had been received, the secretariat and methodologist prepared evidence profiles adapting the DECIDE framework for this purpose. DECIDE is an Evidence to Decision (EtD) framework tool enabling explicit and systematic consideration of evidence on interventions in six domains: effects, values, resources, equity, acceptability and feasibility (11).
As the evidence search was guided by SPICE questions to elicit evidence of what worked or what did not work, rather than the usual PICO format which focuses on evidence of effect, the DECIDE tables were adapted to reflect this. However, the other domains -values, resources, equity, acceptability and feasibility -remained the same in the adapted table.
For each question, the GDG were provided with a summary of the systematic review findings, including an assessment of the quality of that evidence, a summary of the grey literature findings, and findings from both the systematic reviews and grey literature reviews pertinent to values, acceptability, feasibility, equity and resource use. During the guideline development meeting, systematic review teams presented their findings, followed by a presentation of the grey literature findings for each question. Then, using the DECIDE tables as a guide, the GDG discussed the evidence for benefits, harms, feasibility, resource use, values, preferences and equity considerations. Statements summarizing the evidence findings were developed and the GDG decided whether or not these could be formulated as recommendations. If it was agreed that this was an area requiring recommendation, the GDG then further refined the language and set the strength of the recommendation according to the balance of benefits, harms, values, preferences, feasibility, resource and equity considerations.
All decisions were ultimately made by consensus. However, given the limited time available to the meeting and in order to establish the group's position rapidly, an anonymous, instant electronic voting system was provided. Handheld, individual keypads were given to each GDG member and they were asked to vote for different options -usually 'yes' or 'no'. The system only permitted one vote per person per question. When all votes were registered, the group decision appeared on a screen. This allowed the group to either move on when there was clear consensus or open the issue for discussion when there was significant divergence. On several occasions, those who held differing opinions were then able to explain their concerns so cogently that the rest of the group changed their opinion.

# Types of recommendations
Recommendations are statements about what interventions or practices the evidence indicates are the best choices. Not all statements made by the GDG were framed as standard recommendations. In one instance, where there had been inadequate research into an important area of practice, the GDG made a 'research recommendation'. In other instances where there were clear best practices based on accepted principles, but evidence was scarce or indirect, the GDG framed the recommendation as a 'best practice statement'.
As described above, the strength of the recommendation -either 'strong' or 'conditional' -was set by considering the quality of the evidence, the harms, benefits, feasibility, values, preferences, resource use and equity considerations surrounding the recommendation. A strong recommendation is one that should be implemented in all settings, whereas a conditional recommendation is one that may be implemented in specific settings and circumstances.
For one of the questions on how best to ensure sufficient and sustainable financing for ERC, an extensive evidence search found minimal discussion of policies or mechanisms but the GDG decided Statements summarizing the evidence findings were developed and the GDG decided whether or not these could be formulated as recommendations How these guidelines were developed (methodology)
Communicating risk in public health emergencies: a WHO guideline for risk communication (ERC) policy and practice that the grey literature evidence showing how lack of funding hampered ERC, necessitated a strong recommendation (see recommendation B.4. Finance for further discussion). The quality of the evidence was a difficult judgement, as different evidence assessment tools were used, depending on the type of studies providing the evidence (see methods section in Annex 2 for a detailed explanation of tools used to assess the evidence). However, clear 'signals' from the evidence assessment were provided by syntheses of the findings, which were assessed using the different quality of evidence tools described in the methods section above. These were used by the GDG to agree on the quality of the evidence and strength of recommendations. For many of the recommendations, the underpinning evidence was assessed as moderate or low but the panel decided to make a strong recommendation because reported experience (grey literature) and case examples indicated strong benefits, feasibility and positive equity considerations for the actions proposed. A summary of the evidence and other considerations used to develop the recommendations is provided under each of the recommendations in section 7.
Recommendations were developed 'question by question' but it became clear that certain natural, logical groupings of issues and areas of practice were emerging. Hence, the recommendations fall into the following three categories:
No matter how well planned or applied, risk communication interventions will fail to enable people at risk to make informed decisions to act to protect their lives, their health, their families and communities against threats if they do not trust the information source. Therefore, establishing and maintaining trust is arguably the first and most important step in effective ERC. The evidence search confirmed that building trust is inextricably linked to community engagement and open acknowledgement of uncertainty. Hence, the recommendations that were based on the evidence retrieved for the three questions on building trust, communicating uncertainty and community engagement are grouped in this section.

# Building trust and engaging with affected populations

# Trust Systematic review findings (12)
The systematic review found that most studies analysed events in high-and middle-income countries in Asia, Europe, North America and Oceania. The event most often covered was infectious disease; other relatively common events included floods, earthquake, volcanic eruption, bioterrorism, foodborne illnesses, and radiological/radiation emergencies. All four event phases were covered, although there was strong emphasis on the preparation phase, followed by the onset and containment phases, with much less coverage of the recovery phase.
The review found that several factors including organizational messages and actions could predict a higher level of trust, especially: