West Nile Virus: West Nile Virus: Surveillance and Surveillance and

Clinical IssuesClinical IssuesAnne Kjemtrup, DVM, MPVM, Ph.D.Anne Kjemtrup, DVM, MPVM, Ph.D.

California Department of Public HealthCalifornia Department of Public HealthVector-Borne Disease SectionVector-Borne Disease Section 11

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Sequence of WNV detection events in California Sequence of WNV detection events in California relative to human caserelative to human case onset, 2008 onset, 2008

Disease Week of Onset

Num

ber o

f hum

an c

ases

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

0

2

4

6

8

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51

3/21

1/29 6/20

6/27

4/4

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The Clinical “Pyramid Picture”The Clinical “Pyramid Picture”

~80%Asymptomatic

~20%West Nile fever

<1%WNND

~10% of WNND are fatal(<0.1% of total infections)

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West Nile feverWest Nile fever► Typical clinical manifestationsTypical clinical manifestations

►FeverFever►HeadacheHeadache►FatigueFatigue►Muscle weaknessMuscle weakness►Muscle achesMuscle aches►Skin rash on trunk of body Skin rash on trunk of body ►AnorexiaAnorexia

► Duration of illness=3 – 6 daysDuration of illness=3 – 6 days

► Outcome: in general, excellent w/o specific treatmentOutcome: in general, excellent w/o specific treatment

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*Watson JT et al. Ann Intern Med 2004; 141:360-5

Medium Duration of Symptoms in WNV Patients, California and Illinois* Studies Compared

0

10

20

30

40

50

60

70

Symptom

Day

s

California

Illinois

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West Nile Neuroinvasive West Nile Neuroinvasive DiseaseDisease

► Aseptic Meningitis (25%-35% WNND cases)Aseptic Meningitis (25%-35% WNND cases) Fever, headache, malaise, muscle weaknessFever, headache, malaise, muscle weakness Nausea, vomiting, stiff neck, myalgia, cranial nerve palsiesNausea, vomiting, stiff neck, myalgia, cranial nerve palsies Outcome generally goodOutcome generally good

► Encephalitis (60% - 70% WNND cases)Encephalitis (60% - 70% WNND cases) Alternation of consciousness (lethargy Alternation of consciousness (lethargy coma), tremors, coma), tremors,

weakness, brainstem/cranial nerve deficits, cerebellar weakness, brainstem/cranial nerve deficits, cerebellar signs/symptomssigns/symptoms

Outcome variable. Fatality-case ratio up to 15%; increases Outcome variable. Fatality-case ratio up to 15%; increases with advanced age. Potential of long-term neurologic deficits with advanced age. Potential of long-term neurologic deficits in some patients.in some patients.

► WNV “Poliomyelitis”- a flaccid paralysis syndrome WNV “Poliomyelitis”- a flaccid paralysis syndrome (uncommon).(uncommon). Acute onset of asymmetric limb weakness or paralysis in Acute onset of asymmetric limb weakness or paralysis in

absence of sensory lossabsence of sensory loss Can occur in the absence of fever, headache, or other WNV-Can occur in the absence of fever, headache, or other WNV-

associated signs. associated signs. 77

CharacteristicCharacteristicWNFWNFn (%)n (%)

WNNDWNNDn (%)n (%) OROR 95% CI95% CI

DiabetesDiabetes 9 (7)9 (7) 12 (20)12 (20) 3.603.60 1.43 - 9.101.43 - 9.10

Age (>64 years)Age (>64 years) 24 (13)24 (13) 25 (31)25 (31) 2.962.96 1.56 – 5.601.56 – 5.60

HypertensionHypertension 36 (26)36 (26) 26 (44)26 (44) 2.252.25 1.19 – 4.271.19 – 4.27

Gender (male)Gender (male) 114 (62)114 (62) 56 (69)56 (69) 1.361.36 0.78 - 2.370.78 - 2.37

Preliminary Univariate Analysis (2006):Preliminary Univariate Analysis (2006):Risk Factors for Developing WNND vs. WN Risk Factors for Developing WNND vs. WN

FeverFever

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WNV Outcome PictureWNV Outcome Picture

► Risk factors for severe disease include Risk factors for severe disease include increasing age, immunosuppression, increasing age, immunosuppression, diabetes, and hypertension.diabetes, and hypertension. Though risk of WNV infection higher in children Though risk of WNV infection higher in children

than adults, risk of WNND in children lower than than adults, risk of WNND in children lower than adults.adults.

► Most WNF patients recover in first few Most WNF patients recover in first few months. For some, problems may linger months. For some, problems may linger (subclinical encephalitis? Other risk factors?). (subclinical encephalitis? Other risk factors?). ((Encephalitis Outcome Study Shilpa Gavali-Jani, VRDL; Carson Encephalitis Outcome Study Shilpa Gavali-Jani, VRDL; Carson et al., CID 2006; Haaland et al EID 2006et al., CID 2006; Haaland et al EID 2006 ))

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““We’re pretty sure it’s the West Nile virus...”We’re pretty sure it’s the West Nile virus...”

DiagnosisDiagnosis

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West Nile virus West Nile virus Laboratory Testing Laboratory Testing

► West Nile virus (WNV) testing within the regional public health laboratory network is recommended on individuals with the following: A. Encephalitis B. Aseptic meningitis (Note: Consider

enterovirus for individuals ≤ 18 years of age) C. Acute flaccid paralysis; atypical Guillain-

Barré Syndrome; transverse myelitis; or D. Febrile illness

► Illness compatible with West Nile fever and lasting ≥ 7 days

► Must be seen by a health care provider 1111

West Nile virus West Nile virus Laboratory Testing Laboratory Testing

► IgM antibody-capture ELISA for serum collected IgM antibody-capture ELISA for serum collected within 8-14 days of illness onset or CSF collected within 8-14 days of illness onset or CSF collected within 8 days of illness onsetwithin 8 days of illness onset IgM in CSF strong suggests CNS infection since IgM does IgM in CSF strong suggests CNS infection since IgM does

not cross blood-brain barrier.not cross blood-brain barrier.► Plaque-reduction neutralization test (PRNT) used Plaque-reduction neutralization test (PRNT) used

to distinguish false-positive results or cross to distinguish false-positive results or cross reactivity with other arbovirusesreactivity with other arboviruses

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West Nile virus West Nile virus Why test? Why test?

► Differentiate from other conditions (enterovirus, other arboviral diseases)

► Forewarn of further complications (e.g. flaccid paralysis) ► Help with treating/dealing with unexplained lingering health

issues. Early testing in the febrile phase will help determine acute infection.

► A febrile positive WNV patient may have older family members at risk for serious WNV disease (since often acquired near the place of residence) - in effect functioning as a local sentinel.

► Mosquito control and public health agencies can institute proper control measures to save others from serious disease.

► Testing by local health departments is FREE! 1313

TreatmentTreatment► Supportive CareSupportive Care► Experimental: Clinical trial of Experimental: Clinical trial of

interferoninterferon for meningoencephalitis for meningoencephalitis patients underway.patients underway.

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For More Information:For More Information:www.westnile.ca.govwww.westnile.ca.gov

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Where it all began…Where it all began…West Nile Region of West Nile Region of

UgandaUganda

•www.game-reserve.com/uganda_murchison_falls.html •www.min.uni-kiel.de/.../ugandaweb/wnile.html

Mt. Luku IslandmountainMt. Luku Islandmountain

Murchison FallsMurchison Falls

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