APH 1999, 57, 251-262:

Viral infections of the central nervous system: epidemiological and clinical aspects.

P. Cras

Keywords: herpes simplex, encephalitis, epilepsy, acyclovir

Viral encephalitis is a rare but potentially devastating disease characterised by fever, headache, impaired consciousness and focal neurological signs. Herpes simplex 1 encephalitis (HSV-1) is the most common type of viral encephalitis in Belgium. HSV- 1 encephalitis occurs with a worldwide incidence of 0.2 to 0.5/100 000 persons per year without any seasonal variation. lt occurs in patients of all ages, although about one third of patients are younger than 20 and about one half are older te than 50. Both sexes are affected equally. If left untreated, the disease carries a high mortality of about 70%, with many of the survivors showing serious neurological sequelae. Encephalitis caused by other herpes
viridae such as varicella zoster, cytomegalovirus, Epstein-Barr virus, B virus is much less common and tends to occur in particular conditions on such as immunosuppression. Arthropod born encephalitis (Togaviridae, Bunyaviridae, Reoviridae) such as Eastern and Western equine, encephalitis, Japanese encephalitis, Colorado-tick fever and other forms of encephalitis - almost do not occur in Western Europe. Encephalitis caused by mumps virus, rabies, human immunodeficiency virus encephalitis, slow viral infections and rabies are only mentioned here for the sake of completeness. When facing a patient suffering from encephalitis, Mycoplasma pneumoniae should be considered in the differential diagnosis.