Aetiology of encephalitis
The most common cause of encephalitis in Australia is herpes simplex virus. Other causes include varicella zoster virus, Japanese encephalitis virus and Murray Valley encephalitis virus. If the patient has recently travelled overseas, consider Hendra virus, enteroviruses and other pathogens. Listeria monocytogenes infection may present with meningoencephalitis, especially in elderly patients, neonates and patients with immune compromise. Toxoplasma gondii encephalitis can occur, particularly in patients with immune compromise (eg human immunodeficiency virus [HIV] infection). There are also noninfective causes of encephalitis, including autoimmune disorders such as anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis.