West Nile Virus

1
West Nile Virus
Focus on clinical aspects of human infection

• Jo Hofmann, MD
• State Epidemiologist for
• Communicable Disease
• Washington State Department of Health

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
• Parkinsons-like syndromes
• Other neurological manifestations

4
Human infection with WNV
5
West Nile virus infections, by age group
clinical category -- United States, 2003
Source Hayes, N. 5th Natl Conf. on West Nile
Virus, 2004
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
West Nile neuroinvasive disease

• 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)

8
West Nile virus-associated acute flaccid
paralysis (AFP)

• Rare, cases seen during outbreaks
• Symptoms look like poliomyelitis (polio)
• Asymmetrical weakness (left gt 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, wheres my blood meal?
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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
• gt60 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

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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 gt1000 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)

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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

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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 _at_
970-221-6400
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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

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Questions?
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References

• Interim guidelines for the evaluation of infants
  born to mothers infected with West Nile virus
  during pregnancy. MMWR 200453154-7
• Transmission of West Nile virus from an organ
  donor to four transplant recipients. New Engl
  Jour Med 20033482196-2203.
• Possible West Nile virus transmission to an
  infant through breast-feeding - Michigan 2002.
  MMWR 2002 51877-8.

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References

• Petersen LR, Marfin AA. West Nile Virus a primer
  for the clinician. Ann Intern Med 2002137173-9.
• Investigations of West Nile virus infections in
  recipients of blood transfusions. MMWR
  200251973-4.
• Neurologic manifestations and outcome of West
  Nile virus infection. JAMA. 2003290511-5.
• CDC WNV clinical guidance website
• http//www.cdc.gov/ncidod/dvbid/westnile/clinical
  _guidance.htm