AES was a term introduced in 2008 by the World Health Organization to strengthen the surveillance and research of AES in India. AES is characterized by high case fatality rate particularly of children below 15 years. Clinically presents with fever and altered consciousness and rapid worsening of the condition often leading to death. Japanese encephalitis virus (JEV) is the leading diagnosed cause of acute encephalitis, other causes include enteroviruses, scrub typhus, and other viruses circulating in the local area. In many cases, however, no etiological agent is determined, and such cases are categorized broadly as acute encephalitis syndrome (AES). It has been in recent years a pressing public health emergency in India.

Keywords: Encephalitis; Syndrome; fatality; neurologic.