Seizures may be a symptom of the acute illness and can be quite difficult to control.  They may be caused by the inflammation of the brain or by nerve cells not functioning normally.

A significant number of people will develop epilepsy following encephalitis. Most will develop it within the first year or two after the encephalitis, but seizures may also begin much later. The risk of developing epilepsy will depend on the type of encephalitis and whether seizures were part of the acute illness. If seizures were not a symptom of the acute illness, the risk of epilepsy for both adults and children is quite low.  However, even a few acute seizures leads to an increase in the subsequent epilepsy risk.  Some types of encephalitis – such as herpes simplex encephalitis – are more likely to be followed by epilepsy than others. HSE affects the frontal and temporal lobes in particular, which are especially prone to generate seizures if they are damaged.