Eastern equine encephalitis occurs in eastern and southeastern United States; western equine and California encephalitis occur throughout the West; and St. Louis encephalitis occurs throughout the country.
Because of the rarity of Reye's syndrome, it is often misdiagnosed as encephalitis, meningitis, diabetes, or poisoning, and the true incidence may be higher than the number of reported cases indicates.
In secondary encephalitis, symptoms usually begin five to ten days after the onset of the disease itself and are related to the breakdown of the myelin sheath that covers nerve fibers.
Primary encephalitis is caused by direct infection by the virus, while secondary encephalitis is due to a post-infectious immune reaction to viral infection elsewhere in the body.
An increase in WBCs may occur in many conditions, including infection (viral, bacterial, fungal, and parasitic), allergy, leukemia, hemorrhage, traumatic tap, encephalitis, and Guillain-Barré syndrome.