What is new about epidemiology of acute infectious encephalitis?

PURPOSE OF REVIEW This review aims to describe new features on the epidemiology of encephalitis world-wide. As this neurological presentation is most frequently related to transmitted viruses, surveillance of encephalitis is of major importance to detect their emergence or re-emergence. RECENT FINDINGS Rabies causes one of the most severe types of encephalitis as it is lethal in all cases, and it is endemic in some countries. It was thought that the virus had been eradicated in Western Europe, but it re-emerged in Greece and Italy. Physicians should be aware of this diagnosis in the case of severe encephalitis. Some viruses (Powassan, Nipah, and Hendra) are becoming endemic in some new parts of the world (USA and Australia). Because of their severity, they are healthcare concerns in those countries and for travelers (e.g. in Asia). Finally, a concept is emerging: herpes simplex virus is suspected to be a trigger for autoimmune encephalitis. This is of major importance for the future management of patients (corticosteroids early in the course of the disease?), and the epidemiology of sequelae. SUMMARY Encephalitis is a good marker for the detection of emerging infections. New findings about the relationship between herpes simplex virus encephalitis and autoimmune encephalitis open a new concept for a better management of patients.