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Encephalitis is inflammation of the brain tissue. It's most often caused by viral infections. In some cases, bacterial infections can also cause encephalitis.
Etiology. The cause of encephalitis is usually infectious in nature. Viral agents, such as HSV types 1 and 2 (the latter much more common in neonates than adults), VZV, EBV, measles virus (PIE and SSPE), mumps virus, and rubella virus, are spread through person-to-person contact. Human herpesvirus 6 may also be a causative agent.