About one in 150 people will develop severe illness. Those symptoms include high fever, headaches, neck stiffness, stupor, disoriented, coma, tremors, convulsions, muscle weakness, vision loss, numbness and paralysis. Meanwhile, up to 20 percent of people who get sick have much milder symptoms. They include fever, headache, body aches, nausea, vomiting, rash or swollen lymph glands. And here's the important fact to prevent panic. Approximately 80 percent of people who are infected, say four out of every five, will not show any symptoms at all.