This study reports clinico-epidemiological features and viral agents causing acute encephalitis syndrome (AES) in the eastern Indian region through hospital-based case enrolment during April 2011 to July 2012. Blood and CSF samples of 526 AES cases were investigated by serology and/or PCR. Viral aetiology was identified in 91 (17·2%) cases. Herpes simplex virus (HSV; types I or II) was most common (16·1%), followed by measles (2·6%), Japanese encephalitis virus (1·5%), dengue virus (0·57%), varicella zoster virus (0·38%) and enteroviruses (0·19%). Rash, paresis and cranial nerve palsies were significantly higher (P < 0·05) with viral AES. Case-fatality rates were 10·9% and 6·2% in AES cases with and without viral aetiology, respectively. Simultaneous infection of HSV I and measles was observed in seven cases. This report provides the first evidence on viral aetiology of AES viruses from eastern India showing dominance of HSV that will be useful in informing the public health system.

Herpes simplex virus (HSV) infection in the neonatal period may be confined to the eyes, skin and upper aerodigestive tract or may be widely disseminated to other organs, with particular recognition of involvement of the central nervous system (CNS) causing herpes encephalitis (Whitley et al., 1980a, b; Andersen, 1987).

Primary laryngeal HSV infection is extremely uncommon. We present a case of acute neonatal stridor secondary to such localized disease and discuss its management.