#### How common is herpes simplex encephalitis? The wife of a previously healthy 40 year old man requested a domiciliary visit from their general practitioner for her husband, who had been in bed for a few days with “bad flu,” fever, and headache. She was worried that he was becoming quite confused and unable to recall recent events. The GP finds the patient is febrile, agitated, and disoriented in time and place. Concerned about encephalitis, he sends the patient immediately to hospital. There a CT scan shows an area of decreased attenuation in the right temporal lobe and a lumbar puncture a raised lymphocyte count, both suggesting herpes simplex encephalitis. Aciclovir treatment is immediately started. Herpes simplex encephalitis is a severe viral infection of the central nervous system that is usually localised to the temporal and frontal lobes in adults . Typically, it causes a flu-like illness with headache and fever …