Question: which is the most common cause of acute encephalitis in the united states
[{'answer': 'herpes simplex infection', 'provenance': [{'wikipedia_id': '37636', 'title': 'Encephalitis', 'start_paragraph_id': 8, 'start_character': 267, 'end_paragraph_id': 8, 'end_character': 291, 'bleu_score': 1.0, 'section': 'Section::::Cause.:Viral.\n'}]}, {'provenance': [{'wikipedia_id': '37636', 'title': 'Encephalitis', 'start_paragraph_id': 8, 'start_character': 0, 'end_paragraph_id': 8, 'end_character': 381, 'bleu_score': 0.96746874041754, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 17704720615521418909}, 'section': 'Section::::Cause.:Viral.\n'}]}]