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Jo Hofmann's Presentation


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  • 1. West Nile Virus Jo Hofmann, MD State Epidemiologist for Communicable Disease Washington State Department of Health Focus on clinical aspects of human infection
  • 2. Overview and learning objectives
    • Review:
      • Clinical features of human West Nile virus (WNV) infections
      • Routes of WNV transmission in humans
    • Learning objectives
      • Describe symptoms of the most common illness associated with WNV infection
      • Identify the most common route of virus transmission
      • Describe two new methods of surveillance for WNV infections
  • 3. WNV infection: clinical syndromes
    • West Nile fever
      • Mild infection
    • West Nile neuroinvasive disease
      • Meningitis
      • Encephalitis
      • Acute flaccid paralysis (AFP)
        • Polio-like syndrome
      • Movement disorders
        • Involuntary muscle spasms
        • Parkinson’s-like syndromes
      • Other neurological manifestations
  • 4. Human infection with WNV ~80 % No symptoms ~ 20% West Nile fever <1% WNND Fatal WNV infection: <0.1% of all infections 10% of WNND 1/150 of all infections cause West Nile neuroinvasive disease (WNND) Very crude estimates
  • 5. West Nile virus infections, by age group & clinical category -- United States, 2003 Source: Hayes, N. 5th Nat’l Conf. on West Nile Virus, 2004 Washington State Department of Health
  • 6. West Nile fever
    • Self-limited illness with sudden onset
      • Fever, headache, muscle aches, fatigue
      • Nausea, vomiting
      • Rash, swollen lymph nodes
      • Symptoms can be debilitating, may persist for weeks
    • Does not progress to West Nile neuroinvasive disease
  • 7.
    • The disease formerly known as West Nile meningoencephalitis
    • Rarest WNV infection
    • Neurological symptoms occur 1-2 days after onset of fever
    • WNND includes
      • Meningitis - stiff neck, headache, abnormal cerebrospinal fluid
      • Encephalitis - confusion, seizures
      • Acute flaccid paralysis (AFP)
    West Nile neuroinvasive disease
  • 8. West Nile virus-associated acute flaccid paralysis (AFP)
    • Rare, cases seen during outbreaks
    • Symptoms look like poliomyelitis (polio)
      • Asymmetrical weakness (left > right, etc.)
      • No sensory symptoms
      • Abnormal cerebrospinal fluid
    • Affects young, healthy patients compared with other WN neuroinvasive disease
    • Fever, headache may be absent
    • May occur with or w/o meningitis or encephalitis
  • 9. Dude, where’s my blood meal?
  • 10. Newly described routes of WNV transmission
    • Transfusion of blood, platelets, fresh frozen plasma
    • Organ transplantation
    • Perinatal exposure (infected mother to newborn)
    • Breastfeeding
    • Occupational exposure (laboratory accidents, alligator and poultry farming)
  • 11. WNV infections following transfusion
    • First recognized in 2002
    • >60 suspected cases investigated; 23 cases confirmed following transfusion from 16 infected donors
    • Sources: red blood cells, platelets, and plasma
    • Nationwide screening of blood donations began July 2003 – new method of surveillance for WNV infections
  • 12. Screening the blood supply
    • Asking donors about symptoms
    • Screening donations with nucleic acid amplification test (NAAT) – detects virus
    • Contaminated products destroyed, donors contacted
    • Blood banks report infected blood products to state health departments
    • 6.2 million units screened in 2003 – >1000 donors infected with WNV reported
  • 13. Confirmed and probable transfusion-associated WNV infection, 2003
    • Occurred in epicenter of outbreak
      • Three in Texas
      • One each in Nebraska, Iowa, Kansas
    • Onset of symptoms during peak of outbreak: August through October
    • Average age of cases 63 years
    • Five developed WNND (encephalitis)
  • 14. Perinatal transmission of WNV
    • First described in U.S. in 2002
    • Several children born to mothers with confirmed WNV infection
      • Some with neurological defects
    • A large series of cases from 2003-2004 still being investigated
    • CDC has on-line reporting site for registry of pregnancy-associated cases
  • 15. Coming soon: web-based reporting WNV infection during pregnancy: Healthcare providers report on-line States/local HD informed when their providers report Providers contacted for follow-up and specimens needed for testing For now: Call state/local health department or CDC @ 970-221-6400
  • 16. Summary
    • Most WNV infections are asymptomatic
    • Most common illness is West Nile fever
    • The most common route of transmission is through the bite of an infected mosquito
      • Transfusion and pregnancy associated cases
    • Screening of blood donors and web-based reporting of pregnancy associated cases are new surveillance methods
  • 17. Questions?
  • 18. References
    • Interim guidelines for the evaluation of infants born to mothers infected with West Nile virus during pregnancy. MMWR 2004;53:154-7
    • Transmission of West Nile virus from an organ donor to four transplant recipients. New Engl Jour Med 2003;348:2196-2203.
    • Possible West Nile virus transmission to an infant through breast-feeding - Michigan 2002. MMWR 2002; 51:877-8.
  • 19. References
    • Petersen LR, Marfin AA. West Nile Virus: a primer for the clinician. Ann Intern Med 2002;137:173-9.
    • Investigations of West Nile virus infections in recipients of blood transfusions. MMWR 2002;51:973-4.
    • Neurologic manifestations and outcome of West Nile virus infection. JAMA. 2003;290:511-5.
    • CDC WNV clinical guidance website: