Hand, foot and mouth disease is an acute infectious disease caused by enterovirus. Most severe cases are caused by enterovirus 71 (EV71) infections, which are dangerous and have a high mortality rate. Early identification of severe cases of EV71 infection requires attention to the following indicators: 1. persistent high fever: body temperature (axillary temperature) greater than 39 ℃, conventional antipyretic effect is not effective. 2, neurological manifestations: mental depression, vomiting, easily startled, shaking limbs, weakness, unstable standing or sitting, etc., very rare cases appear hyperphagia. 3. Respiratory abnormalities: increased, decreased or irregular rhythm of breathing. If the respiratory rate in a quiet state exceeds 30-40 times/min (according to age), neurogenic pulmonary edema should be alerted. 4.Circulatory dysfunction: cold sweat, cold extremities, skin pattern, increased heart rate (>140-150 beats/min, according to age), increased blood pressure, and prolonged capillary refill time (>2 seconds). 5.Elevated peripheral blood WBC count: peripheral blood WBC over 15×109/L, except for other infectious factors. 6. Elevated blood glucose: stress hyperglycemia with blood glucose >8.3 mmol/L is present. Early cerebrospinal fluid examination should be performed in cases with suspected neurological involvement. Hospitals with conditions should check for EV71 virus antibodies as early as possible. Antibodies can appear positive in the early stage of EV71 virus infection. Children with positive antibodies should be closely observed for mental status, limb tremors, easy startle, skin temperature, and respiration, heart rate, and blood pressure, and recorded in a timely manner, which is a key point in the screening of severe cases of EV71 infection.