Sudden high fever
Severe headache
Stiff neck
Nausea or vomiting
Sensitivity to light
Confusion or trouble concentrating
Drowsiness or hard to wake up
Seizures
Rash that does not fade when pressed
Cold hands and feet
Fast breathing
Muscle or joint pain
Loss of appetite
Irritability
In babies: poor feeding
In babies: unusual crying
In babies: bulging soft spot on the head
In babies: floppy or very stiff body
In babies: being hard to comfort
Seek emergency medical care right away if these symptoms appear