Is the virus the same strain as last month’s outbreak in Surrey?

Tests are continuing, but experts believe so. It might have been spreading in sheep. Foot-and-mouth symptoms in sheep are similar to another common complaint known as orf. But state vets tested thousands of animals without finding evidence of disease. The vaccine strain is relatively weak and there may be a longer incubation period.

How else could it have spread?

The incubation period is a week to ten days. We do not know when the infected cattle were moved to the field at Milton Park Farm. It was after the August Bank Holiday weekend as the field was the venue for the Royal Egham Show on August 25 and 26 and livestock were banned. Deliberate sabotage by an aggrieved worker or eco-terrorist remains a possibility. The virus can survive for 50 days in the environment in soil, grass and in water, especially in humid weather. It can also last 14 days in dry faeces and 39 days in urine.

How else could the cattle have contracted the disease?

The most likely transfer of the virus from Pirbright laboratories to the farm at the centre of last month’s outbreak is thought to be on tyres of lorries contaminated at the site by waste effluent from a leaking pipe.

Could it be elsewhere?

Yes, and that is why government vets are urgently tracing movements of people, vehicles and animals connected with the latest farm.

What is the worst scenario?

That the disease has spread to pigs, which are the biggest transmitters of the disease because they breathe out large quantities of the virus.

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