FOAMed

A 13-year-old male presents to the ED for aggressive behavior which progressed to confusion and decreased level of consciousness. He initially was very agitated and aggressive and refused to drink any water. He then became disoriented and is now difficult to rouse. The parents note that he had recently had a fever, sore throat, and general malaise prior to this behavior but those symptoms resolved, although they note excessive salivation. Review of systems is remarkable for a bat bite for which he never sought care. He is tachycardic, tachypneic, febrile, and appears toxic. What’s the most likely diagnosis?