<P> Viral encephalitis can occur either as a direct effect of an acute infection , or as one of the sequelae of a latent infection . The majority of viral cases of encephalitis have an unknown cause , however the most common identifiable cause of viral encephalitis is from herpes simplex infection . Other causes of acute viral encephalitis are rabies virus , poliovirus , and measles virus . </P>
which is the most common cause of acute encephalitis in the united states
herpes simplex infection