Encephalitis can cause flu-like symptoms, such as a fever or severe headache. It can also cause confused thinking, seizures, or problems with senses or movement. However, many cases of encephalitis result in only mild flu-like symptoms or even no symptoms. Severe cases of encephalitis, while relatively rare, can be life-threatening. Because the course of any single case of encephalitis can be unpredictable, it's important to get a timely diagnosis and treatment.