Encephalitis is a serious brain disorder in which the nervous system, especially the brain, becomes swollen.
The NHS says the condition can be 'life-threatening' and requires urgent hospital treatment if contracted.
The disease usually starts with flu-like symptoms, such as high fever and headache, but can quickly develop more severe symptoms.
These include: confusion/disorientation, seizures/seizures, changes in personality and behavior, difficulty speaking, weakness, and loss of consciousness
It's not always clear how someone can get encephalitis, but viral, bacterial, and fungal infections can cause the disease.
Some types of encephalitis can be spread by ticks, mosquitoes and mammals, although it is not possible to contract the disease from someone else.
Ticks that spread the disease are found in most of Europe, including the United Kingdom, Russia and several parts of China and Japan.
In Britain, only a small number of ticks carry the disease, meaning there is a low risk of becoming seriously ill after a tick bite.
A vaccine against the disease is available. Two injections can protect a person for about a year, while three injections protect people for about three years.