General Discussion

Human contraction of the virus may lead to asymptomatic infection, acute respiratory infection or fatal encephalitis. Clinical signs typically manifest within 3–14 days which include fever and headache, often accompanied by a cough, throat soreness, difficulty breathing, and other common signs of respiratory illness.[16] Patients may also initially present with symptoms of myalgia and vomiting.[17]

This can be followed by dizziness, drowsiness, altered consciousness, and neurological signs that indicate acute encephalitis. Some people can also experience atypical pneumonia and severe respiratory problems, including acute respiratory distress. Encephalitis and seizures occur in severe cases, progressing to coma within 24 to 48 hours.[16][17]

The incubation period is from 4 to 14 days but an incubation period as long as 45 days has been reported.[17]

Death occurs in 40–75% of cases, and some long-term side effects of infection include persistent convulsions and personality changes. Most survivors make a full recovery, although some are left with residual neurological conditions after acute encephalitis. Some cases of relapse have been reported.[17]