A Flavvuridae arbovirus, WNV is capable of infecting humans. Birds are the primary reservoir host of the virus while humans and other mammals are dead end hosts incapable of directly transmitting the disease. Humans can also acquire WNV through blood transfusions, organ transplantation, laboratory exposure, or from mother to child in utero or through breastmilk. Approximately 80% of WNV cases are asymptomatic.Symptoms including fever, headache, tiredness, rash, diarrhea, muscle pain, and nausea and vomiting. These symptoms appear three to 14 days post-infection. In severe cases WNV can cause high fever, coma, tremors, severe seizures, paralysis, and death. Case fatality rates for severe WNV infections range from three to 15 percent, but most asymptomatic cases are unreported. Treatment of WNV cases is symptomatic, and no human vaccine currently exists for the virus. Severe cases often require hospitalization and palliative care. Mild cases of WNV resolve in less than one week, with recovery in severe cases taking up to several months. In some cases, such as paralysis, those infected by WNV never completely recover.