Spread mainly by midge bites, the virus was in the first recorded case in the UK in 17 years.
This strain was introduced into Cornwall from midges blown in wind from northern France but scientists believe the virus likely spread rapidly after overwintering in parts of the UK.
The outbreak has hit the agriculture sector hard and.
Jerry Sanders-Carr, who runs Exe Valley Lamb, near Exeter, said he had lost 15% of his sheep to the virus.
"Talking to some of the guys who've been going out picking up large numbers of dead animals every morning, some of these guys I'm sure there's going to be a lasting impact on them," he said.
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