Encephalitis is the inflammation of the brain which may be characterized by flu-like symptoms, seizures, confusion, and difficulties in moving or sensing. Among children, the symptoms include bulging of the fontanels, nausea, vomiting, stiffness, irritability, and difficulty in feeding. The exact cause is generally unknown but it is often due to viral infection such as those involving herpes virus, enterovirus, mosquito-borne viruses (West Nile, La Crosse, and St. Louis mosquitoes), tick-borne viruses, and rabies virus. Encephalitis may also be caused by other inflammations and bacterial infections.
There are two types of encephalitis: primary and secondary. Primary encephalitis occurs when a virus or bacteria directly infects the brain. Secondary encephalitis occurs when the immune system incorrectly reacts to an infection by attacking the healthy brain cells instead of only targeting the unhealthy cells. This usually manifests two or three weeks after the first infection.