It is important to seek immediate medical attention if you suspect that you have encephalitis. The key symptoms are fever, severe headache, and confusion.

Other symptoms that may occur include:

• Abnormal sensitivity to light (photosensitivity).
• Nausea and vomiting.
• Stiff neck and back.
• Lack of energy, sluggishness (lethargy).
• Drowsiness.

More serious symptoms can also develop, including:

• Seizures or tremors.
• Personality changes.
• Memory loss.
• Trouble learning and understanding.
• Restlessness.
• Confused speech.
• Hallucinations, which is seeing or hearing things that aren't there.
• Delirium, which is a sudden change in your mental status, leading to confusion and unusual behavior.

The most severe form of encephalitis can lead to coma and even death, especially if left untreated. In general, symptoms that develop suddenly and are severe from the start are more likely to progress to a life-threatening case of encephalitis.

Although complications such as speech or memory problems can occur, most people fully recover from encephalitis when treated promptly. However, your chances for a full recovery decrease if you have severe symptoms, such as seizures or coma, or if you delay treatment.¹

The early stage of encephalitis may cause symptoms similar to meningitis, a serious viral or bacterial illness that causes inflammation of the tissues that surround the brain and spinal cord.