title: Emerging Cases of Powassan Virus Encephalitis in New England: Clinical Presentation, Imaging, and Review of the Literature.
abstract: BACKGROUND
  Powassan virus (POWV) is a rarely diagnosed cause of encephalitis in the United States. In the Northeast, it is transmitted by Ixodes scapularis, the same vector that transmits Lyme disease. The prevalence of POWV among animal hosts and vectors has been increasing. We present 8 cases of POWV encephalitis from Massachusetts and New Hampshire in 2013-2015.
  
  
  METHODS
  We abstracted clinical and epidemiological information for patients with POWV encephalitis diagnosed at 2 hospitals in Massachusetts from 2013 to 2015. We compared their brain imaging with those in published findings from Powassan and other viral encephalitides.
  
  
  RESULTS
  The patients ranged in age from 21 to 82 years, were, for the most part, previously healthy, and presented with syndromes of fever, headache, and altered consciousness. Infections occurred from May to September and were often associated with known tick exposures. In all patients, cerebrospinal fluid analyses showed pleocytosis with elevated protein. In 7 of 8 patients, brain magnetic resonance imaging demonstrated deep foci of increased T2/fluid-attenuation inversion recovery signal intensity.
  
  
  CONCLUSIONS
  We describe 8 cases of POWV encephalitis in Massachusetts and New Hampshire in 2013-2015. Prior to this, there had been only 2 cases of POWV encephalitis identified in Massachusetts. These cases may represent emergence of this virus in a region where its vector, I. scapularis, is known to be prevalent or may represent the emerging diagnosis of an underappreciated pathogen. We recommend testing for POWV in patients who present with encephalitis in the spring to fall in New England.
authors.affiliation: Division of Infectious Disease, Massachusetts General Hospital.
authors.forename: Anne
authors.initials: A
authors.lastname: Piantadosi
authors.affiliation: Department of Neurology, Brigham and Women's Hospital, Boston.
authors.forename: Daniel B
authors.initials: DB
authors.lastname: Rubin
authors.affiliation: Department of Infectious Diseases, Lahey Hospital & Medical Center, Tufts University School of Medicine, Burlington.
authors.forename: Daniel P
authors.initials: DP
authors.lastname: McQuillen
authors.affiliation: Department of Radiology.
authors.forename: Liangge
authors.initials: L
authors.lastname: Hsu
authors.affiliation: Division of Infectious Disease, Massachusetts General Hospital.
authors.forename: Philip A
authors.initials: PA
authors.lastname: Lederer
authors.affiliation: Division of Infectious Disease, Brigham and Women's Hospital, Boston, Massachusetts.
authors.forename: Cameron D
authors.initials: CD
authors.lastname: Ashbaugh
authors.affiliation: Christiana Care Health System, Division of Infectious Diseases, Newark, Delaware.
authors.forename: Chad
authors.initials: C
authors.lastname: Duffalo
authors.affiliation: Department of Infectious Diseases, Lahey Hospital & Medical Center, Tufts University School of Medicine, Burlington.
authors.forename: Robert
authors.initials: R
authors.lastname: Duncan
authors.affiliation: Department of Neurology, Brigham and Women's Hospital, Boston.
authors.forename: Jesse
authors.initials: J
authors.lastname: Thon
authors.affiliation: Department of Neurology, Brigham and Women's Hospital, Boston.
authors.forename: Shamik
authors.initials: S
authors.lastname: Bhattacharyya
authors.affiliation: Division of Infectious Disease, Massachusetts General Hospital.
authors.forename: Nesli
authors.initials: N
authors.lastname: Basgoz
authors.affiliation: Department of Neurology, Brigham and Women's Hospital, Boston.
authors.forename: Steven K
authors.initials: SK
authors.lastname: Feske
authors.affiliation: Department of Neurology, Brigham and Women's Hospital, Boston.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Lyons
mesh_terms: D000212:Acyclovir / Q000627:therapeutic use; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D000914:Antibodies, Viral / Q000134:cerebrospinal fluid; D000998:Antiviral Agents / Q000627:therapeutic use; D001921:Brain / Q000000981:diagnostic imaging / Q000473:pathology / Q000821:virology; D004669:Encephalitis Viruses, Tick-Borne / Q000187:drug effects / Q000276:immunology / Q000472:pathogenicity; D004675:Encephalitis, Tick-Borne / Q000175:diagnosis / Q000000981:diagnostic imaging* / Q000453:epidemiology* / Q000821:virology; D005260:Female; D005416:Flavivirus / Q000187:drug effects / Q000276:immunology / Q000472:pathogenicity; D006801:Humans; D018884:Ixodes / Q000821:virology; D008279:Magnetic Resonance Imaging; D008297:Male; D008404:Massachusetts / Q000453:epidemiology; D016920:Meningitis, Bacterial / Q000188:drug therapy; D008875:Middle Aged; D009513:New Hampshire / Q000453:epidemiology; D015995:Prevalence; D012621:Seasons; D014481:United States / Q000453:epidemiology; D055815:Young Adult
chemical_list: D000914:Antibodies, Viral; D000998:Antiviral Agents; D000212:Acyclovir
keywords: New England; Powassan; deer tick virus; encephalitis