What causes encephalitis?

Updated: Aug 07, 2018
  • Author: David S Howes, MD; Chief Editor: Barry E Brenner, MD, PhD, FACEP  more...
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The cause of encephalitis is usually infectious in nature. Viral agents, such as HSV types 1 and 2 (the latter much more common in neonates than adults), VZV, EBV, measles virus (PIE and SSPE), mumps virus, and rubella virus, are spread through person-to-person contact. Human herpesvirus 6 may also be a causative agent. [4] The CDC has confirmed that WNV can be transmitted by means of organ transplantation and via blood transfusions.

Important animal vectors include mosquitoes and ticks, which spread the arbovirus group, and warm-blooded mammals, which are vectors for rabies and lymphocytic choriomeningitis (LCM).

Bacterial pathogens, such as Mycoplasma species and those causing rickettsial disease or catscratch disease, are rare and invariably involve inflammation of the meninges out of proportion to their encephalitic components. Encephalitis due to parasites and fungi other than Toxoplasma gondii are covered elsewhere.

Noninfectious causes include the demyelinating process in acute disseminated encephalitis.

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