Although not everyone with viral encephalitis exhibit symptoms, some people may develop symptoms that mimic the flu, including fatigue, weakness, aches in joints or muscles, fever and headache, according to Mayo Clinic. When encephalitis is more severe, seizures, muscle weakness, paralysis in areas of the body or face, loss of sensation, hallucinations, agitation and confusion can result. Other symptoms include loss of consciousness, trouble hearing or speaking, altered perception of smell and double vision.
Symptoms of encephalitis in young children and infants are slightly different. Symptoms to watch for include vomiting, nausea, body stiffness and irritability. Poor feeding or not remaining awake during feeding may also occur. Babies may cry inconsolably, and a bulge may be noticed in the fontanels of infants' skulls; these are the so-called "soft spots."
When severe symptoms are noticed, it is important that emergency care is sought immediately. Altered consciousness, fever and severe headache are particularly ominous signs that should be evaluated right away. Any symptoms in children or babies should also be treated as an emergency.
Although encephalitis' exact cause is not known, it is usually caused by a viral infection. Still, it can be caused by noninfectious inflammatory conditions and bacterial infections too, as noted by Mayo Clinic.