Predicting the spread of foot and mouth disease by airborne virus.

Foot and mouth disease (FMD) can spread by a variety of mechanisms which, under certain climatic and epidemiological conditions, includes the windborne spread of disease. Recent advances in knowledge of the aerobiological features of FMD are described. The strain of virus and species of infected animal are major determinants of airborne virus emission. Pigs emit most virus, cattle and sheep lesser but similar amounts to each other. Peak excretion of airborne virus by sheep occurs before the clinical phase of disease, whereas with cattle and pigs, it coincides with the development of early clinical disease. The probability of aerogenous infection differs greatly between livestock species. Cattle are the most susceptible, followed by sheep, whereas pigs are very resistant. Computer-based simulation models have been developed to analyse and predict the risk of airborne spread of FMD and have been used successfully during outbreaks to support decision-making. Further research is required to refine and extend the models for operational use.