Les encéphalites infectieuses aiguës : recommandations pour un diagnostic étiologique

Despite a better knowledge of pathophysiology, and a wider use of new molecular technologies for the diagnosis, the etiological diagnosis of acute encephalitis is not assessed in most cases. Incidence, prognosis, rate and severity of sequellae remain unknown to date. In France, according to the published data, the incidence of encephalitis is estimated to an average of 1.9 case/100,000 inhabitants in non human immunodeficiency virus (HIV) patients. The aetiological diagnosis is assessed in less than 30% of cases. The most frequent diagnosis is herpetic encephalitis in adults, and encephalitis due to varicella-zoster virus (VZV) in children under 16. Despite a difficult diagnosis and the lack of specific treatment for most of those infections, the aetiological diagnosis should always be deeply explored to assess the individual prognosis, to allow a better management of antibiotic therapy and to improve epidemiological knowledge. We present the recommendations established by the French Society of Infectious Diseases. First designed to fit the French epidemiology, they take into account the potential exposure of patients to different epidemiological patterns. Three levels of aetiological tests are proposed to assess the diagnosis of the most common infections and those, which require immediate treatment, as well as the rarest ones.