A Defra report today concluded that the Pirbright site where the Merial Animal Health and the Institute for Health are located is the most likely source of infection.
The initial findings of National Emergency Epidemiology Group which has been investigating the outbreak also goes on to identify the possible mechanisms for spread of the virus from the Pirbright site.
It concludes that the risk of spread of infection out of Surrey through movements of undisclosed infection in sheep during the risk period is very low. It sets out the most likely scenario that while there is a risk of further cases in the same area, it is unlikely that infection from the original release of the virus will occur, however, further cases could arise from secondary spread.
Defra chief veterinary officer Debby Reynolds said: "The decision not to vaccinate at this stage, but to retain our full readiness to do so, demonstrates that our contingency planning arrangements are working. The epidemiology report indicates that infection may be contained to the Surrey area. But, these are our emerging findings, this is a developing situation and new information may come to light at any stage which changes our understanding of the outbreak."
"It is therefore crucial that all animal keepers continue with the most stringent biosecurity measures, remain vigilant and contact their own veterinarian or local Animal Health Office if they have any concerns."