Category:Rapid Risk Assessment

Once an incident has been verified as a potential public health concern, a rapid risk assessment is undertaken (usually within 24 to 48 hours) to evaluate the risk to human health. The risk to a population from a communicable disease depends on the likelihood of transmission in the population (probability) and the severity of the disease (impact). The probability of an incident developing and the impact, if it does, is based on the nature of the infectious agent and the details of the incident. This may be further influenced by context or the broad environment in which the incident occurs, including political, public, and media interest, perception of threat, and the acceptance of risk, which may vary between countries and cultures.

Rapid risk assessment is a core part of public health response and, thus, widely undertaken by public health professionals. Formal systems that grade evidence and recommendations, such as the systematic methods used in evidence-based medicine, rely on published research evidence. Studies are graded according to design and susceptibility to bias. However, as time and evidence are limited, a rapid risk assessment may need to rely at least partly on specialist expert knowledge, and these formal systems are not directly applicable.

There are only a limited number of examples of a more systematic and transparent approach to rapid risk assessment in the literature, including:

• a qualitative method for assessing the risk from emerging infections in the UK (Morgan et al. 2009) using algorithms to consider the probability of an infection occurring in the UK population, its potential impact, and identifying gaps in knowledge or data;
• a prioritization approach to rank emerging zoonoses posing the greatest threat in the Netherlands, based on seven criteria (including the probability of introduction, the likelihood of transmission, economic damage, morbidity, and mortality) to aid decision-making (http://www.rivm.nl/bibliotheek/rapporten/330214002.html);
• a dynamic risk assessment model developed in the UK to assess the risk from an outbreak or incident, consisting of five attributes (severity, spread, confidence in the diagnosis, ease of intervention, and the wider context in which events are occurring) rated over a 0 to 4 scale. During an outbreak, the dynamic risk assessment of each event occurring is used to inform management action at that time (http://hpzoneinfo.infact.com/HPZone/RiskAssessment/tabid/58/Default.aspx)

However, transparency, explicitness, and reproducibility principles also apply to a rapid risk assessment. For the rapid risk assessment of most infectious disease threats, observational data is often the only available and obtainable source of information. Expert knowledge is also important if there is a lack of time and evidence. In such cases, it is important to ‘unpack’ and make explicit the expert knowledge and distinguish between knowledge based on good research and experience and opinion-based knowledge. Serious attempts should be made to assess the quality of the evidence-based on the source, design, and quality of each study or piece of information.

Uncertainties should be identified, clearly documented, and communicated, and the assessment updated in light of new evidence.

A rapid risk assessment includes the approach and tools required at each stage of the process:

- stage 0 is the preparation stage; 
- stage 1 is the collection of event information; 
- stage 2 is the literature search and systematic collection of information about the etiological agent; 
- stage 3 focuses on the extraction of evidence; 
- stage 4  conducts an appraisal of the evidence, 
- and stage 5 estimates the risk. Transparency and sharing of information are essential at every stage. This document incorporates a step-by-step guide through each stage with examples and checklists of the resources and evidence required. 

Advance preparation and planning save time and is vital to ensure that potential threats are identified, assessed, and managed effectively. Ideally, the following should be in place:

• evidence-based protocols and guidance for responding to incidents,
• protocols for identifying sources of key information for rapid risk assessment,
• strategies for literature searches,
• and lists of relevant contacts, including named experts.

Rapid risk assessments of potential communicable disease threats can be complex and challenging as they must be produced quickly when information is often limited and circumstances can evolve rapidly. The rapid risk assessment methodology described in this document enables the structured identification of key information using a systematic appraisal of the best scientific evidence and/or specialist expert knowledge available at the time to provide a clear estimate of the health risk scale. This is important in not only communicating the potential magnitude of the risk in a systematic and transparent way but also allowing documentation of evidence and gaps in knowledge when the assessment is made.

References

This text is the entire executive summary of a technical document published by ECDC:

• Operational guidance on rapid risk assessment methodology. ECDC Technical Document. August 2011.