Forest encephalitis is an acute infectious disease of the central nervous system caused by a tick-borne encephalitis virus of the genus Flavivirus, for which ticks are the vector of transmission. Clinical manifestations are divided into four main phases: Phase I, the incubation period, is usually 10-15 days. The second phase, the prodromal phase, is characterized by low-grade fever, dizziness, malaise, general malaise, and aching limbs. If the patient has an acute onset, it will reach its peak in 1-2 days. In the third phase, acute phase, there are mainly symptoms of fever, which is usually high, reaching 39-41℃, and will last for 5-10 days in most patients. It also shows symptoms of systemic toxicity, mainly flushing of the face and neck, conjunctival congestion, and slow pulse. Some patients with severe disease may show signs of myocarditis, including increased heart rate and T-wave changes on electrocardiogram. In severe cases, there will also be disorders of consciousness and mental impairment, such as lethargy, indifferent expression, blurred consciousness, coma, and also delirium and confusion. Some also show manifestations of meningeal involvement, most commonly severe headache, with pain in the temporal region as well as in the posterior occipital region, sometimes explosive and fluctuating. Muscle paralysis is less common in the lower extremity muscles and facial muscles, and is more common in the neck muscles, scapular muscles and upper extremity joint paralysis. Other manifestations of neurological damage include tremors and involuntary movements. In the fourth stage, the recovery period, usually about 10 days on average, the body temperature drops, the limb paralysis gradually recovers, the mental state becomes lighter, and various symptoms gradually disappear.