Herpes Viruses
Encephalitis refers to an inflammation of the brain, and typically results from a viral infection. According to the "Journal of American Medical Association," the most common cause of viral encephalitis in the United States is herpes simplex virus type 1, the herpes virus that causes cold sores. Other herpes viruses that can cause encephalitis are herpes simplex type 2 (genital), varicella-zoster virus (chickenpox and shingles) and Epstein-Barr virus (mononucleosis).
Childhood Infections
Several common childhood infections besides chickenpox can lead to a secondary infection of viral encephalitis, according to the Mayo Clinic. These include measles (rubeola), mumps and German measles (rubella). All these infections are now vaccine-preventable, so cases of secondary encephalitis due to these illnesses have become rare.
Arboviruses
Arboviruses are viruses transmitted to humans from other animals by tick and mosquito bites. Types of arboviruses that can spread encephalitis include Eastern equine encephalitis, which usually afflicts birds and horses and averages fewer than 10 cases per year. Western equine encephalitis typically afflicts horses and is found rarely in humans. St. Louis encephalitis is transmitted to mosquitoes by birds and has an average of 130 cases reported each year. La Crosse encephalitis is transmitted to humans via mosquitoes from squirrels and chipmunks; there are fewer than 100 cases per year. West Nile encephalitis is found typically in birds but has been transmitted, in rare cases, human to human through blood transfusions, organ transplants, from mother to unborn child or through breastfeeding. Encephalitis has also been transmitted to humans through bites from rabid animals.
