West Nile Virus: Where Are We Now

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West Nile Virus Where Are We Now?

• James J. Sejvar, MD
• Division of Vector-Borne Infectious Diseases
• and
• Division of Viral and Rickettsial Diseases
• National Center for Zoonotic, Vectorborne, and
  Enteric Diseases
• Centers for Disease Control and Prevention

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West Nile Virus Epidemiology The National
Perspective
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1999
2000
2001
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WNV Neuroinvasive Disease Incidence, by County,
US, 2002
N2,946
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WNV Neuroinvasive Disease Incidence, by County,
US, 2003
N2,866
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WNV Neuroinvasive Disease Incidence, by County,
US, 2004
N1,148
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WNV Neuroinvasive Disease Incidence, by County,
US, 2005
N1,309
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WNV Neuroinvasive Disease Incidence, by County,
US, 2006
N1,491
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Reported WNV Disease Cases in Humans,United
States, 1999-2006
Plus D.C.
Reported as of 02/25/2007
Onset Dates 2 JAN 30 DEC
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Reported WNV Disease Cases in Humans,United
States, 1999-2006
Plus D.C.
Reported as of 02/25/2007
Onset Dates 2 JAN 30 DEC
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WNV U.S. Numbers in Perspective

• WNVnow the most common cause of arboviral
  encephalitis in Western hemisphere
• Estimated number of U.S. citizens infected since
  1999 1.2 million
• Therefore, gt299 million still susceptible to
  infection / disease...
• Future epidemiologic pattern unclear

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WNV Clinical Illness
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WNV Human Infection Iceberg
lt1 CNS disease
20 West Nile Fever

• Asymptomatic Infection
• 80 of infections
• Generation of life-long immunity (presumed)

80 Asymptomatic
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WNV Human Infection Iceberg
lt1 CNS disease

• West Nile Fever
• 10-30 of infections
• Fever, headache, rash, fatigue

20 West Nile Fever

80 Asymptomatic
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WNV Human Infection Iceberg

• WNV Neuroinvasive Disease (WNND)
• 1 of all infections
• Meningitis, encephalitis, poliomyelitis

1 CNS disease

20 West Nile Fever
80 Asymptomatic
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WNV Acute Clinical Illness

• Increased age (gt55), immunosuppression
  independent risk factors for neuroinvasive
  disease
• Acute case fatality in WNND 15 20
• Movement disorders
• Tremors
• Parkinsonism
• WN Poliomyelitis particularly severe
• Limb paralysis syndrome akin to poliovirus
  infection
• CFR gt50 with respiratory involvement
• Prolonged institutionalization, rehabilitation
  among survivors

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WNV The Other Iceberg
Acute WNV Illness
WNV Long-term effects
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WNV Long-Term Outcomes

• West Nile Fever Persistent symptoms common
• Chicago 2002 63 of 98 WNF patients with
  persistent symptoms at 30 days median duration
  of symptoms 60 days
• Colorado 2005 Quality of life measures (SF-36)
  significantly reduced among 16 WNF patients at 2
  years post-infection
• West Nile Encephalitis Persistent disabling
  neurologic sequelae
• Tremors, movement disorders, cognitive problems
  in gt50
• gt1.5 years after acute illness
• Higher mortality rates gt1 year post-infection

Watson et al. Ann Intern Med, 141 2004
Sejvar et al., in press,
Greenberg et al., EID 2005
Carson et al., CID 2006
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WNV Long-Term Outcomes

• West Nile Poliomyelitis
• High acute mortality
• Prolonged ventilatory support, institutionalizatio
  n among those with respiratory weakness
• Iron lung
• Severe long-term weakness
• Recovery in only 1/3 of 23 patients by 2 years
• Young, healthy people often affected
• Loss of productive years

Sejvar et al, EID 2006
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WNV Summary

• Future epidemiologic pattern unclear, but
  significant endemic / epidemic activity likely
• WNV associated with substantial morbidity and
  mortality in the short term, particularly in
  high-risk groups
• WNV increasingly associated with long-term
  effects lasting years (even in mild illness)
• Evolving issues
• Alternative modes of transmission (blood
  transfusions, solid organ transplants)
• Treatment (MAbs, antivirals)
• Vaccine development (cost-effectiveness?)
• Genetics / host factors associated with WNND

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