Japanese Encephalitis is caused by a group of virus known as arbovirus. Arboviruses (arthropod-borne viruses) are a large group of viruses that are spread mainly by blood-sucking insects like mosquitoes. Birds are often the source of infection for mosquitoes, which can then spread the infection to horses and other animals.

Man is an incidental host. However man-to-man transmission of the disease is not possible.

More about the causative organism: Arbovirus

Arbovirus is short for arthropod-borne virus. This virus is found all over the world. The presence of an arbovirus in a particular area depends on the availability of specific types of mosquitoes that can carry it and specific birds or animals that can be infected.

Arboviruses can cause four types of illness:

Illnesses of the central nervous system, ranging in seriousness from mild viral meningitis to encephalitis (inflammation of the brain), with coma, paralysis, and death

Mild fever illnesses with or without rash

Hemorrhagic fevers that can be serious and life-threatening

Arthritis and rash, with or without fever