This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Medicine
Commonest cause of sporadic encephalitis is: 
Select and explain. 
A. Japanese B Virus, B. Herpes Simplex Virus, C. Human Immunodeficiency Virus, D. Rubeola Virus
B: Herpes Simplex Virus
Answer: B: Herpes Simplex Virus 
Explanation: Answer is B (Herpes simplex encephalitis): The most common cause of sporadic viral encephalitis is HSV-1