Aetiology and Laboratory Diagnosis of Acute Encephalitis Syndrome with Special Reference to India

Acute encephalitis syndrome (AES) which encompasses infections of the central nervous system (CNS), such as encephalitis, meningitis, and meningoencephalitis, is quite commonly encountered in clinical practice and contributes to significant mortality and morbidity in the community. Several organisms including viruses, bacteria, fungi, and parasites are known to cause AES in humans. The cardinal clinical and laboratory findings are largely similar regardless of the causative agent and consist of fever, headache, and altered mental status, which are often accompanied by seizures and focal neurological abnormalities. Therefore, identification of the causative pathogen is paramount in AES, as rapid detection and confirmation of aetiological agent will have a tremendous impact on the management of outbreaks as well as patient’s illness. This article reviews the aetiological and laboratory diagnostic aspects of AES with special reference to the Indian context.