Known causes of encephalitis may include viruses (i.e. West Nile virus, rabies, measles) or bacteria, fungi, and parasites. As the brain tissue swells, nerve cells may be destroyed which can result in brain damage. Initial symptoms may include a fever, headache, and/or low energy, but may also include more serious symptoms such as confusion, muscle weakness, loss of consciousness, and sudden changes in mental functions. Encephalitis may result in complications with memory, speech, processing speed, hearing, muscle coordination and personality changes.