Encephalitis
Encephalitis, any infectious disease of the human central nervous system characterized by inflammation of the brain . The typical symptoms are headache , fever , and extreme lethargy, which lead eventually to coma ; double vision, delirium , deafness , and facial palsy often occur in the acute stage of the disease. Aftereffects of encephalitis may include deafness, epilepsy , and dementia. Several types of encephalitis are caused by viral infection of the central nervous system. These types fall into two main groups, primary neurotropic-virus infections (original virus infections in nerve tissues), and secondary infections occurring as complications of a primary virus infection elsewhere in the body. NEUROTROPIC-VIRUS ENCEPHALITIS This group comprises several epidemic diseases that primarily affect wild and domestic animals and birds. The disease is transmitted to humans from these animals by insect vectors. St. Louis encephalitis, first recognized in 1933 during an epidemic in S