Encephalitis in children is caused by cold, decreased resistance to immunity, strong virulence and high number of pathogens. The ubiquitous bacteria and viruses can invade the body through the respiratory tract, digestive tract, skin and other channels, multiply in the body, reach all parts of the body through blood circulation, and can cause infections in all parts of the body. For example, in pediatrics, lung infection is called pneumonia, intestinal infection is called enteritis, and infection caused by bacteria and viruses entering the brain through the blood-brain barrier is commonly known as encephalitis, which is a blood infection of encephalitis; some other infections are direct infections, such as infections of tissues adjacent to the brain, such as otitis media and mastoiditis, which spread easily to the meninges and cause septic meningitis; there are also some viruses of the optic nerve, such as herpes simplex virus, which can spread through the olfactory nerve and cause septic meningitis. Herpes simplex virus via the olfactory nerve and varicella-zoster virus via the sensory nerve endings reach the nerve trunk and invade the brain, causing viral encephalitis. Encephalitis is also common in children because of their low immune function and underdeveloped nervous system. If a child has encephalitis, he or she needs to be seen and treated promptly to avoid delays.