title: Incidence and mortality of herpes simplex encephalitis in Denmark: A nationwide registry-based cohort study.
abstract: We aimed to investigate the incidence and mortality of herpes simplex encephalitis (HSE) in a nationwide cohort.
  
  
  
  From the Danish National Patient Registry, we identified all adults hospitalised with a first-time diagnosis of HSE in Denmark during 2004-2014. The HSE diagnoses were verified using medical records and microbiological data. Patients were followed for mortality through the Danish Civil Registry System. We estimated age-standardised incidence rates of HSE and 30-day, 60-day, and 1-year cumulative mortality. Furthermore, we assessed whether calendar year, age, gender, level of comorbidity, virus type, and department type was associated with HSE mortality.
  
  
  
  We identified a total of 230 cases of HSE. Median age was 60.7 years (interquartile range: 49.3-71.6). The overall incidence rate was 4.64 cases per million population per year (95% confidence interval: 4.06-5.28). The cumulative mortality within 30 days, 60 days, and 1 year of the HSE admission was 8.3%, 11.3%, and 18.6%, respectively. Advanced age and presence of comorbidity were associated with increased 60-day and 1-year mortality.
  
  
  
  This nationwide study of verified HSE found a higher incidence than reported in previous nationwide studies. Presence of comorbidity was identified as a novel adverse prognostic factor. Mortality rates following HSE remain high.
authors.affiliation: Department of Infectious Diseases, Aarhus University Hospital, Palle Juul-Jensen Boulevard 99, 8200 Aarhus N, Denmark. Electronic address: laujoerg@rm.dk.
authors.forename: Laura Krogh
authors.initials: LK
authors.lastname: Jørgensen
authors.affiliation: Department of Infectious Diseases, Aarhus University Hospital, Palle Juul-Jensen Boulevard 99, 8200 Aarhus N, Denmark. Electronic address: Lars.Dalgaard@skejby.rm.dk.
authors.forename: Lars Skov
authors.initials: LS
authors.lastname: Dalgaard
authors.affiliation: Department of Infectious Diseases, Aarhus University Hospital, Palle Juul-Jensen Boulevard 99, 8200 Aarhus N, Denmark. Electronic address: larsoest@rm.dk.
authors.forename: Lars Jørgen
authors.initials: LJ
authors.lastname: Østergaard
authors.affiliation: Department of Clinical Epidemiology, Aarhus University Hospital, Oluf Palmes Allé 43-45, 8200 Aarhus N, Denmark. Electronic address: mn@clin.au.dk.
authors.forename: Mette
authors.initials: M
authors.lastname: Nørgaard
authors.affiliation: Department of Infectious Diseases, Aarhus University Hospital, Palle Juul-Jensen Boulevard 99, 8200 Aarhus N, Denmark; Department of Biomedicine, Aarhus University, Vennelyst Blvd. 4, 8000 Aarhus C, Denmark. Electronic address: trinmoge@rm.dk.
authors.forename: Trine Hyrup
authors.initials: TH
authors.lastname: Mogensen
mesh_terms: D000368:Aged; D015331:Cohort Studies; D015897:Comorbidity; D003718:Denmark / Q000453:epidemiology; D020803:Encephalitis, Herpes Simplex / Q000453:epidemiology* / Q000401:mortality* / Q000821:virology; D005260:Female; D006561:Herpes Simplex / Q000150:complications / Q000453:epidemiology* / Q000401:mortality / Q000821:virology; D006760:Hospitalization; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D012042:Registries; D012189:Retrospective Studies
keywords: Comorbidity; Epidemiology; Herpes simplex encephalitis; Herpes simplex virus; Incidence; Mortality; Prognosis; Viral encephalitis