https://phys.org/news/2019-01-uk-vigilant-bluetongue-lucky.html

A new paper published in Scientific Reports suggests that a combination of geographic location, weather conditions and existing animal movement restrictions helped limit the impact of the 2007 UK outbreak to just 135 farms.

Bluetongue is believed to have entered the UK in southeast England, an area with relatively low farm density, meaning that opportunities for infected midges to spread between farms were fewer than they might have been elsewhere. "Had the virus entered the UK in the west of England then the outbreak would probably have been much larger," says study author Dr. Joanne Turner from the Institute of Infection and Global Health.