Comparison of clinical manifestations, outcomes and cerebrospinal fluid findings between herpes simplex type 1 and type 2 central nervous system infections in adults.

In previous reports on the viral causes of central nervous system (CNS) infections, it has been generally recognized that HSV-1 is a major cause of encephalitis, while HSV-2 is the predominant cause of aseptic meningitis in adults. To examine this matter, the clinical characteristics in the two types of HSV CNS infections were investigated. In a retrospective cohort study which included all adult patients (≥16 years) between January 1999 and December 2013 in a 2,700-bed tertiary care hospital, all the patients in whom PCR of the CSF for HSV was positive were identified. Ninety-five patients with positive CSF PCR results for HSV were included, 21 with HSV-1 and 74 with HSV-2. Many patients with HSV-1 had encephalitis (13/21, 61.9%), whereas most patients with HSV-2 had meningitis (62/74, 83.8%). However, HSV-1 and HSV-2 accounted for similar proportion of patients with HSV encephalitis (13/25, 52.0% vs. 12/25, 48.0%). Neurological sequelae were more frequent among patients with HSV-1 (9/21, 42.9% vs. 6/74, 8.1%; P = 0.001). The present study suggests that HSV-2 is not only a major cause of aseptic meningitis, but also it may cause serious manifestation as HSV-1 encephalitis in adults.