While the majority of West Nile infections are mild and asymptomatic, approximately 20% of those infected will develop symptoms such as fever, headache, body aches and swollen glands. The more severe West Nile encephalitis is estimated to occur in one out of every 150 infections. Symptoms include high fever, neck stiffness, stupor, convulsions, coma and sometimes paralysis. Death can occur in the most severe cases when the virus crosses the blood-brain barrier, leading to encephalitis or inflammation of the brain.