What is Encephalitis?

Encephalitis is an inflamation of the brain and spinal cord usually caused by viral infection. Diseases such as rabies, polyomelitis, and herpes encephalitis are all caused by virus infections that affect the brain and spinal cord and are transmitted in a variety of ways. Arboviral encephalitis refers to similar maladies that are transmitted by arthropods, mainly mosquitoes. Although the majority of cases of arboviral encephalitis infection are asymptomatic or have only very mild symptoms, the disease can sometimes damage nerves and can cause lasting damage and even death. Symptoms include sudden fever, headache, vomiting, unusual visual sensitivity to light, stiff neck and back, confusion, drowsiness, clumsiness, difficulty walking, and irritability.

Arboviral encephalitides are maintained in nature in complex life cycles involving a nonhuman primary vertebrate host and a primary arthropod vector and which usually do not include humans. Humans and domestic animals can contract the disease when the virus escapes the cycle and infects a secondary host. This can happen because of ecological or demographic changes, or due to population changes in the primary vector, host, or both. Many arboviruses that cause encephalitis have a variety of different vertebrate hosts and some are transmitted by more than one vector.

There are five major types of arboviral encephalitis in the United States: