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Encephalitis, an inflammation of the brain caused by infectious or autoimmune processes, affects an estimated 500,000 to 1.5 million people globally each year and causes approximately 100,000 deaths annually. Despite advances in treatment, many survivors experience long-term cognitive, physical, and psychological effects that can profoundly affect quality of life.
The review, led by researchers from the Nuffield Department of Clinical Neurosciences, University of Oxford, and the Mayo Clinic, Florida, considers the latest evidence on the diagnosis, treatment, prevention, and long-term outcomes of encephalitis. Dr Sophie Binks, Clinical Lecturer at the Nuffield Department of Clinical Neurosciences, and lead author of the review, said:
Encephalitis is a form of brain inflammation and a potentially devastating condition causing severe symptoms such as seizures, cognitive and behaviour change. Early recognition and treatment are vital to achieve the best outcomes for patients.”
The review highlights how understanding of encephalitis has changed dramatically over the past two decades. While infectious causes such as herpes simplex virus remain common, researchers have identified an expanding range of autoimmune forms of encephalitis, in which the immune system mistakenly attacks the brain.
Autoimmune encephalitis is now recognised to be at least as common as infectious encephalitis in many high-income countries. Advances in antibody testing have enabled clinicians to identify previously unexplained neurological syndromes and offer targeted immunotherapies that can significantly improve patient outcomes.
The researchers emphasise that diagnosis should be guided by careful clinical assessment alongside rapid testing of blood and cerebrospinal fluid. They argue that infectious and autoimmune causes should be investigated in parallel to avoid delays in treatment.
The review also highlights emerging global challenges. Climate change, urbanisation, and changes in the distribution of disease-carrying insects are increasing the risk of some forms of infectious encephalitis, including West Nile virus and Japanese encephalitis virus. At the same time, declining vaccine uptake threatens progress against vaccine-preventable causes of brain inflammation.
The researchers call for greater investment in diagnostic infrastructure, physician education, public awareness, and international surveillance systems. They also highlight the need for better rehabilitation services and long-term support for survivors, many of whom continue to experience difficulties with memory, concentration, mood, employment, and social participation long after the acute illness has resolved. Dr Binks added:
It was an honour to be first author on the team for this prestigious Lancet review, and particularly important to highlight encephalitis in a global and general medical journal, since patients present worldwide and to many specialties including, for example - as well as of course my own specialty of neurology - general medicine, emergency departments, psychiatry, and infectious diseases.
I am proud to be continuing Oxford's world-leading heritage in encephalitis research to progress our understanding of this condition, with the aim of improving knowledge of susceptibility factors and optimal treatments.”
A Q&A with senior author, Professor Sarosh Irani, by the Mayo Clinic.