Previous PageTable Of ContentsNext Page

Risk analysis for Rift Valley Fever


Risk analysis is something that people do intuitively in their everyday lives and in their professional work. Only recently has it developed into a more formal discipline that is being used increasingly in many fields. In animal health it has perhaps been most widely applied in quarantine. Quarantine risk analyses are used for helping to decide the most appropriate health conditions for imported animals and animal products and for strategies for quarantine operations.

Risk analysis is a tool that can also be used to very good advantage for animal disease emergency preparedness planning. In this context, it is most readily applied to preparedness planning for exotic diseases (or exotic strains of endemic disease agents) and it will be described for this purpose in this chapter. However, there is no reason why risk analysis cannot be applied to other animal health emergency planning.


Risk analysis comprises four components: risk identification, risk assessment, risk management and risk communication.

In the first component, the risks of an event occurring or of taking a particular course of action are identified and described. The likelihood of these risks occurring is then estimated. If risks do occur, their potential consequences are evaluated and used to modify the risk assessment. For example, if an exotic disease has a high risk of entry to a country, but only a low risk of establishment there or trivial potential socio-economic consequences, it will only get a low overall score on a risk assessment. Conversely, a low risk of introduction but significant consequences of the disease will be rated more highly.

Risks can be assessed in a quantified, semi-quantified or qualitative way. It is inherently very difficult to quantify (or actually put probability numbers to) risks in many biological systems because of the lack of historical precedents and serious gaps in available biological data. Risks should be quantified as far as is practicable. If this cannot be done, qualitative risk assessments are recommended for exotic diseases. Risks can be described as extreme, high, medium and low, or qualified by a simple scoring system, for example, 1-5 for both the level of risk and for the degree of potential consequences. This will help to establish a prior ranking for identified risks, which will provide a solid platform for contingency planning.


The risk assessment component is best carried out by the Epidemiological Unit in the National Veterinary Service as part of the national early warning system for TADs and other emergency diseases. Risk management and risk communication are tasks for everyone, but should be coordinated by the chief veterinary officer (CVO).

It should be remembered that risks do not remain static. They will change with factors such as climate change; evolution and spread of epidemic livestock diseases internationally; emergence of new diseases; and changing international trading patterns in the country. Risk analysis should therefore not be regarded as a one-off activity but be repeated and updated regularly.

Risk analysis for RVF should be considered on a regional basis and not purely at the national level. The determinants of factors conducive to RVF epizootic activity are, for example, the characteristics of the intertropical convergence zone (ITCZ) in Africa, the Southern Oscillation index and remote sensing satellite data (RSSD) such as cold cloud density (CCD), the normalized differentiated vegetation index (NDVI) and basin excess rainfall monitoring systems (BERMS). These are regional and continental climatic factors that affect large areas of Africa. Coordinated networking of such information needs to be undertaken by EMPRES, the Intergovernmental Authority on Development (IGAD), the United Nations Development Programme (UNDP) and other agencies with monthly bulletins assessing the ongoing levels of risk.


As described above, risk assessment consists in identifying the risks, assessing the likelihood of their occurrence and modifying them by an evaluation of their potential consequences.

The international status and evolution of outbreaks of RVF (and other important TADs) as well as the latest scientific findings should be constantly monitored. Analysis of this information should be a routine function of the Epidemiological Unit of the National Veterinary Service. Apart from the scientific literature, the most valuable source of information is the International Office of Epizootics (OIE), for example through its weekly disease reports, the annual OIE World Animal Health and the OIE HandiSTATUS database. Disease intelligence is also available from FAO, particularly in the EMPRES Transboundary Animal Diseases Bulletin, which is published quarterly (and is also available on the Internet at The Program for Monitoring Emerging Diseases (ProMED), an Internet server and mailing service, currently provides a useful forum for rapid dissemination of official and unofficial information on animal, plant and human disease occurrences around the world. Information may also be obtained from designated OIE and FAO experts and reference laboratories and from regional animal health groups.

Having identified and listed the exotic disease threats, the next step is to assess the seriousness of the threat of entry of each disease to the country and the routes and mechanisms by which the disease may enter. Relevant questions to be answered for RVF include the following:

The next step is to evaluate how serious the socio-economic and public health consequences might be if the disease occurs. There are a number of questions to be answered:

By addressing these questions and issues it will be possible to build up a risk profile for RVF and judge the magnitude of the risk presented by the disease in qualitative, if not quantitative, terms. It will also be possible to get an idea of how RVF ranks in relation to other high-priority risk diseases, and decide what resources need to be devoted to preparedness for RVF in comparison with other diseases. Possible pressure points for entry and/or occurrence of the disease can be ascertained, showing where preventive and disease surveillance activities need to be strengthened, and establishing whether the veterinary services and contingency planning are adequate to deal with the risk.

It is clear that many risk factors will vary over time, which is one of the many reasons why this manual needs to be periodically reviewed.


The type of risk assessment described will help to:

Previous PageTop Of PageNext Page