As the virus passes along to the brain and then to the spinal cord, initial symptoms are fever, fatigue, headache, vomiting, stiffness in the neck, and pain in the limbs.
Kui viirus on jõudnud peaajju ja seejärel seljaajju, on esmasteks sümptomiteks palavik, kurnatus, peavalu, oksendamine, kaela jäikus ning valu jäsemetes.