Genus - alphaherpes. Pathogenesis is not well understood. Occurs usually in adults and it may be the consequence of reactivation from trigeminal ganglion, or secondary infection. High mortality if untreated. Acyclovir has made a difference on outcome.
Early diagnosis is important - brain biopsy most definitive method.
These are RNA viruses with envelope. Cause a hemorrhagic disease with encephalitis. Note that an outbreak of West Nile virus occurred in New York City and in New York State in 1999-2000. Family - Bunyaviridae. Note that Hantaviruses are also members of the Bunyaviridae.