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UIC School of Public Health October Deans Forum: West Nile Virus Update

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Title: UIC School of Public Health October Deans Forum: West Nile Virus Update


1
UIC School of Public HealthOctober Deans
Forum West Nile Virus Update
  • Dan Tessier Doug Passaro

2
What is West Nile Virus (WNV)?
  • Arbovirus (arthropod-borne virus)
  • Flavivirus family Yellow Fever, Dengue, St.
    Louis Encephalitis Viruses
  • Transmitted among various species of birds
    primarily through mosquitoes (Culex and others)
  • 1937 Isolated from blood of woman in West Nile
    district, Uganda

3
What is West Nile Virus (WNV)?
  • 1957 cause of encephalitis (spinal cord and
    brain infection) in elderly patients during
    outbreak in Israel.
  • 1960s Horse infections Egypt France
  • Currently endemic in Africa, the Middle East, and
    Southwestern Asia

4
Human/Equine Epidemics
  • Israel 1951-54, 57 Congo 1998
  • France 1962 Italy 1998
  • South Africa 1974 Russia 1999
  • Algeria 1994 USA 1999-02
  • Romania 1996-97 Israel 2000
  • Morocco 1996 France 2000

5
A New Disease? NYC, 1999
WNV
  • Massive die-off of local birds
  • Sudden, unusual cluster of encephalitis (SLE?)

Bird Disease same as Human Disease?
Birds confirmed with WNV
Humans confirmed with WNV
August 1999
September 1999
6
Lanciotti et al. Science 2862333-337
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Lanciotti et al. Science 2862333-337
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Lessons from NYC Outbreak
  • Serosurvey 6 weeks after outbreak peak
  • 2.6 infected with WNV
  • 0.5 non-specific West Nile fever
  • 1 of 5 infected persons
  • 0.02 developed West Nile Encephalitis
  • 1 of 140 infected persons
  • RISK FACTOR spending time outdoors near dawn and
    dusk
  • PROTECTIVE using insect repellent

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NYC, 2001
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WNV dead bird Forest preserve
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WNV dead bird Forest preserve
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National, through 2001
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National, through 2002
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National, through 2002
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WNV Spectrum of Illness
  • Most infections clinically silent
  • Milder illness non-specific flu-like symptoms
  • Prominent myalgias, backaches, arthralgias
  • Occasional rash (20), lymph node swelling
  • Severe illness
  • Aseptic meningitis Fever, headache, stiff neck
  • Encephalitis Mental changes ? coma, death
  • Myelitis Polio-like, fever with flaccid
    paralysis
  • Elderly/immunocompromised at high risk
  • Diabetics, Hypertensives

22
Laboratory Findings
  • Total WBC usually normal or ?
  • Low WBC and anemia also occurrs
  • Serum sodium sometimes ?
  • Examination of cerebrospinal fluid (CSF) typical
    for a viral meningoencephalitis
  • Lymphocytes in CSF
  • Protein ?, Glucose normal

23
Radiographic Imaging
  • CAT scans mostly normal
  • Magnetic resonance imaging (MRI) ? inflammation
    of leptomeninges, the periventricular areas, or
    both

24
Diagnosis
  • West Nile virus or viral RNA in serum,
    cerebrospinal fluid, or other tissue.
  • Isolation from culture (insensitive 3-7 days)
  • RNA detection/PCR (insensitive)
  • West Nile virus protein can be identified in
    brain specimens by immunohistochemical staining
    (IHC)

25
Diagnosis
  • IgM Antibody-Capture Enzyme-Linked ImmunoSorbent
    Assay, (MAC-ELISA 24-36 hrs)
  • IgM in cerebrospinal fluid confirmatory
  • IgM in serum not specific
  • IgG (PFNR assay) acute convalescent serum

26
Outcomes
  • Case-fatality rates (hospitalized)
  • 4 Romania,
  • 12 New York,
  • 14 Israel,
  • Similar (12) among Northeast US patients
    2000/2001, and IL patients 2002
  • lt50 of hospital patients return to functional
    level by discharge only 1/3 fully ambulatory

27
Outcome 1 Year Later
  • Fatigue, 67
  • Memory loss, 50
  • Walking difficulties, 49
  • Muscle weakness, 44
  • Depression, 38

28
Treatment of WNV Encephalitis
  • Supportive hospitalization, fluids, respiratory
    support, and prevention of secondary infections
  • Therapeutic Ribavirin Interferon ?2b have
    activity against WNV in vitro
  • No controlled studies of these or other
    medications (steroids, immune globulin)
  • Vaccines a few years off?
  • An ounce of prevention . . .

29
1975
1975
Lyme disease first recognized Jimmy Hoffa
disappeared Movie Jaws Song Feelings
30
St. Louis Encephalitis, 1975 Background
  • Illinois
  • 1964 Southern IL (Hamilton County)
  • 1968 Saline County
  • Then no activity until 1974.
  • Tennessee
  • 1965 Memphis-Shelby County HD began annual
    bleeding of birds for SLE ab testing
  • 1974 increased prevalence in birds noted early
    summer ? intensified mosquito control
  • gt50 confirmed human cases followed, 5 deaths
  • Other clusters Birmingham AB, and Mexico

31
1975 SLE Outbreak
  • 2,131 documented cases (30 states D.C.)
  • 578 (27 of total) in Illinois
  • 67 (66) Illinois counties reported cases
  • gt50 in metropolitan Chicago
  • Newspaper Headlines
  • Sleeping sickness kills four
  • Encephalitis at epidemic stage in Cook County
  • City, county crews join mosquito war

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2001 Déjà vu all over again.
  • 2001 Illinois dead bird WNV surveillance 8/02 -
    10/02
  • Crows, blue jays, raptors
  • 138/284 (49) tested positive
  • Culex mosquito pools tested in Cook County
  • 20/81 pools positive
  • Horses - 2 positive of 9 symptomatic

35
Preliminary Positive WNV Test Results,
Illinois,2002
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Differences Between SLE and WNV
  • WNV better adapted to northern temperatures
    Ontario grows 2X faster than SLE
  • WNV may produce higher viremia in birds
  • WNV kills many birds and horses
  • WNV identified in many non Culex species

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Risk of WNV Illness
  • of mosquitos X
  • Prevalence in mosquitos (0.5-5) X
  • of bites per mosquitos life X
  • Risk that a bite transmits wnv X
  • Risk of severe illness if infected (1/150)
  • 1/30,000 bites??

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