Once inside the blood stream the virus is carried around the body until it finds a place where it can start to develop the disease. Even if the midge does not have the virus, it can become infected itself through pumping up blood from a sheep that is already infected. The disease, bluetongue, affects the mouth and tongue. It is often fatal. Bluetongue virus is made up of several layers surrounding a ball of chromosomes.
Bluetongue is found in hot countries and sometimes gets as far as Spain.
It does not occur in the UK, because it is too cold for the midges to survive.