Viral encephalitis in travellers.

Viral infections are the commonest cause of encephalitis, and the purpose of this article is to inform UK clinicians of the presentation, diagnosis and management of viral encephalitis in travellers returning to the UK. The classical presentation is as a triad of fever, headache and altered mental state. There may be other findings either on examination or on imaging which, together with a travel history, may give clues as to the aetiology. It is important to note that in high- and middle-income countries the commonest cause of viral encephalitis is herpes simplex. This, coupled with the fact that untreated herpes simplex encephalitis (HSE) has a mortality of over 70%, means that aciclovir should always be included in the treatment of patients with suspected encephalitis, regardless of their history of travel. In the UK, the Rare and Imported Pathogens Laboratory (RIPL) at Public Health England can perform specific polymerase chain reaction (PCR) analyses on blood and CSF samples for many imported causes of viral encephalitis.