Box 1.

Definitions (as used in research studies)4

Encephalopathy = (altered consciousness persisting for longer than 24 h, including lethargy, irritability or a change in personality or behaviour)
Encephalitis = encephalopathy AND evidence of CNS inflammation, demonstrated by at least two of:
  • fever

  • seizures or focal neurological findings attributable to the brain parenchyma

  • CSF pleocytosis (more than 4 white cells per μL)

  • EEG findings suggestive of encephalitis

  • neuroimaging findings suggestive of encephalitis.

  • CNS = central nervous system; CSF = cerebrospinal fluid; EEG = electroencephalography