Encephalitis

Encephalitis is the inflammation of the brain by blood-borne immune cells. It is not to be confused with neuroinflammation, which is the modern inflammation of the nervous system by tissue-resident immune cells. Unlike with neuroinflammation, encephalitis is associated with swelling of the brain and can be detected using magnetic resonance imaging (MRI).

Encephalitis is normally caused by a virus, vaccine or when something else that causes inflammation. Encephalomyelitis is when the inflammation affects the spinal cord as well as the brain.

Viral encephalitis
More than 90% of viral encephalitis is caused by herpes simplex virus (HSV), varicella-zoster virus (VZV), and enteroviruses.

List of all known viruses associated with encephalitis:
 * adenovirus
 * cytomegalovirus
 * encephalomyelitis virus (Western equine or Eastern equine)
 * Ebola virus
 * Epstein-Barr virus
 * enteroviruses including coxsackieviruses, echo viruses and poliovirus
 * flaviviruses, which causes Japanese encephalitis
 * herpes simplex
 * herpes zoster virus (shingles)
 * La Crosse Virus, causing La Crosse or California encephalitis
 * lassa virus
 * lymphocytic choriomeningitis virus
 * measles
 * Murray Valley encephalitis virus
 * rabies virus
 * Rocio virus
 * rubella
 * St. Louis encephalitis virus, a flavivirus
 * varicella zoster virus (chickenpox)
 * Venezuelan equine encephalitis virus
 * West Nile virus

Research
In 2020, the Open Medicine Foundation announced a study investigating brain fog in patients with herpes simplex encephalitis, including following those patients over time to see which developed ME/CFS.

Learn more

 * Encephalitis - Merck Manuals
 * Viral encephalitis - Better Health, Australia
 * ICD-11 - World Health Organization