Infection of the new crown is characterized by fever, dry cough and malaise. Some patients may have nasal congestion, runny nose, sore throat, decreased or loss of smell and taste, conjunctivitis, myalgia and diarrhea as the main manifestations. Severe patients tend to develop respiratory distress or hypoxemia one week after the onset of the disease, and in severe cases, the disease may rapidly progress to acute respiratory distress syndrome, septic shock, uncorrectable metabolic acidosis and coagulation dysfunction and multi-organ failure. Patients with mild forms of the disease may present with low-grade fever, mild malaise, and impairment of the sense of smell and taste, with no signs of pneumonia. There may be no clinical symptoms after infection with the novel coronavirus. Asymptomatic and mild cases are predominant in vaccinated patients and those infected with Omicron. Clinical symptoms mainly include low to moderate fever, dry throat, sore throat, nasal congestion, runny nose, and other symptoms of upper respiratory tract infection. Most patients have a good prognosis, but a few patients are in critical condition, mostly in the elderly, people with chronic underlying diseases, late pregnancy and perinatal women, and obese people. Symptoms in children are relatively mild, and some children and newborns may have atypical symptoms, such as vomiting, diarrhea and other gastrointestinal symptoms, or only poor response and shortness of breath. A very small number of children may have a multi-system inflammatory syndrome (MIS-C), with Kawasaki disease-like or atypical Kawasaki disease manifestations, toxic shock syndrome, or macrophage activation syndrome, which most often occurs during the recovery period. The main manifestations are fever with rash, non-purulent conjunctivitis, mucosal inflammation, hypotension or shock, coagulation disorders, and acute gastrointestinal symptoms. Once it occurs, the condition can deteriorate dramatically in a short period of time.