Encephalitis can occur either during or after a measles infection. This can happen as a result of the brain becoming infected with the virus during the rash phase of the illness or by an immune-mediated brain inflammation subsequent to measles infection. (1)

There are different types of measles encephalitis depending on the stage of the rash. (2)

  • Primary measles encephalitis when encephalitis is concurrent with measles infection (the brain becomes infected during the rash phase of the infection).
  • Acute post-measle encephalitis when encephalitis is caused by immune-mediated brain inflammation subsequent to measles infection (occurs 2–30 days after infection).
  • Measles inclusion body encephalitis most commonly occurs in immunodeficient children (within 1 year of measles infection). It leads to death in 75% of cases.
  • Subacute sclerosing panencephalitis (SSPE) is a progressive and fatal central nervous system disease occurring following reactivation of the measles virus (6-15 years after measles infection).