The incubation period is 1-4 days, mostly 3-7 days, based on the current epidemiological evidence. Fatigue, and dry cough are the most common clinical onset symptoms. Nasal congestion, sore throat, and diarrhea are atypical clinical presentations. Patients with mild or moderate type only demonstrate a low fever and mild fatigue without pneumonia in the early stage of disease. Most patients have a good prognosis, with few patients becoming critically ill. Prognosis is poor for the elderly and those with chronic underlying diseases, and the symptoms of children tend to be relatively mild.