Tick-Borne Encephalitis Virus

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Dr. Miller presented a perplexing case of a middle-aged otherwise healthy woman who presented with subacute progressive headache, neck pain, fevers, and malaise which subsequently improved for 4-5 days prior to relapsing and progressing to overt confusion. Her CSF studies revealed a nonspecific lymphocytic pleocytosis and elevated protein count with normal glucose and CSF viral PCR, VRDL, AFB, CrAg, and cultures all negative. It was discovered that she recently traveled to Moldova, where Tick-Borne Encephalitis Virus is endemic, and for which her syndrome proved relatively classic. The CSF is pending at the CDC for confirmatory testing.

Tick-Borne Encephalitis Virus

  • Member of the Flaviridae
    • 3 closely related viruses: Russian spring-summer encephalitis subtype, Siberian subtype (Vasilchenko virus), Central European encephalitis subtype (Western Subtype)
  • Vectors include the tick species Ixodes persulcatus, Ixodes ricinus in Russia and Europe
  • Similar pathogens include West Nile virus, Powassan virus
  • Incubation period 7-28 days (poorly defined)
  • Biphasic illness:
    • Viremic phase: fever, fatigue, malaise, headache, arthralgia
    • Neurologic phase: can range from mild meningitis to severe encephalitis; myelitis, flaccid paralysis
  • CSF: pleocytosis, predominantly mononuclear cells
  • Dx: IgM Ab from the CSF or PCR, serum IgM Ab
  • Treatment: supportive

Some learning points from this case:

  • Consider tick-borne encephalitis virus in patients with compatible travel history and biphasic syndrome
  • If you are concerned about endemic disease in an area of the world with which you are not familiar, remember the CDC's Yellow Book (excellent online resource with country-specific health information)
  • Don't forget the social history!

Thanks again to Dr. Miller for an excellent review of Tick-Borne Encephalitis Virus.