Defining causality in acute brain infections

Determining the likelihood of causation by a pathogen in brain infections such asencephalitis and meningitis is challenging. While case definitions published forencephalitis causation for a UK-based study in 2010 have been used widely, there havebeen advances in diagnostic methods and clinical understanding since then, and theywere not designed for use globally nor for patients with meningitis or brain abscess. Wepresent an update to these case definitions, based on a systematic review of theliterature for each pathogen, and extend them to include pathogens of greaterrelevance to low- and middle-income country settings as well as to other brain infectionsyndromes. Emerging pathogens are also included, and more detailed instructions foruse of the definitions are provided.