Is an inflammation of the brain caused by a virus. The major risk is permanent brain damage. Children aged one year or less and adults aged 55 years and over are at increased risk of life threatening complications. Encephalitis symptoms can appear within 2 days to 2 weeks of exposure to the virus. Many people who are infected do not develop any symptoms. In milder cases, symptoms may resemble the flu. In severe cases of encephalitis, symptoms may include: