Li Ching-yun notes that most people who contract the disease have mild symptoms, or don't show any symptoms at all. A smaller number of people will suffer from lassitude, difficult breathing, and vomiting; and in the worst cases life-threatening encephalitis, pulmonary edema and paralysis.
李慶雲指出，多數人的癥狀都很輕微，甚至不發病，少數較嚴重的病患有活動力差、呼吸困難、嘔吐等癥狀，有引發致命的腦炎、麻痺、肺水腫等嚴重併發症的危險。