Monte Carlo simulation of virus introduction into the Netherlands

In order to improve the understanding of the risk of introducing classical swine fever (CSF) and foot-and-mouth disease (FMD) into the Netherlands, a Monte Carlo simulation model was developed. The model, VIRiS (Virus Introduction Risk Simulation model) describes virus introduction into the Netherlands from outbreaks in other European countries. VIRiS is aimed at supporting decision makers involved in disease prevention. The model is based on historical and experimental data, supplemented with expert judgement, and provides the expected number, location and cause of primary outbreaks in the Netherlands. The paper gives a detailed description of the design and behaviour of VIRiS. The default outcomes of VIRiS show that in the current situation, the western and northern regions of the Netherlands are most prone to outbreaks of CSF and FMD. Most outbreaks originate from the countries neighbouring the Netherlands and the countries of southern Europe. Several alternative prevention strategies were evaluated using a combination of the VIRiS model and models describing the spread and economic consequences of outbreaks. A considerable financial window is available for measures aimed at speeding up the detection of epidemics in countries from which a Dutch outbreak may originate. Complete elimination of the risk associated with the risk factor 'returning trucks' reduces the annual losses due to FMD and CSF epidemics by approximately US$ 9 million. The approach is general and could also be applied to other diseases and countries.