WEST NILE VIRUS (WNV) A Growing Concern

WEST NILE VIRUS (WNV) A Growing Concern

WEST NILE VIRUS (WNV)A Growing Concern George A. Fisher, PA-C, MPH, DFAAPAOctober 25, 2012West Nile VirusObjectives

Be familiar with the prevalence of the West Nile Virus

Know the etiology, signs and symptoms, and treatment for infections from West Nile Virus

Be familiar with methods to prevent acquiring infections from West Nile Virus

Origins1937 - First isolated in the West Nile District, Uganda

1950s Presence described in Egypt

1957 Severe human encephalitis in elderly (Israel)

1960s Equine disease 1st noted in Egypt and France

1999 First appearance of WNV in North America in humans and horsesWest Nile Virus (Arbovirus)

West Nile VirusSingle- Stranded RNA virus (Flavivirus genus)

Arbovirus (Arthopod-borne)

Member of Japanese encephalitis virus complexJapanese EncephalitisSt Louis EncephalitisMurray Valley Encephalitis

Since 1999 very few genetic changes in US strains (versus influenza strains)

West Nile Virus - Transmission

West Nile Virus - TransmissionAlternate Routes (very small proportion of cases)Transplanted organsBlood transfusionsBreastmilk (one probable case)TransplacentalOccupational Exposure (two lab workers)WNV- Culex species

Distribution of OutbreaksHuman Encephalitis1994 Algeria1996-97 Romania1997 Czech Republic1998 Democratic Republic of Congo1999 Russia1999-2003 United States2000 - Israel

Distribution of OutbreaksEquine Disease

1996 Morocco

1998 Italy

1999-2001 United States

2000 - FranceDistribution of OutbreaksBird Disease

1997-2001 Israel

1999-2002 United States

(since 1999 WNV activity in humans, birds, veterinary or mosquitoes has been reported in all states except: Hawaii, Alaska and Oregon)

WNV Human DiseaseMild DiseaseWest Nile Fever

Severe DiseaseWest Nile MeningitisWest Nile EncephalitisWest Nile Poliomyelitis

West Nile FeverIncubation Period

2 to 14 days(documented longer in immunosuppressed population)Clinical Features(only 20% develop symptoms) PrimaryFeverHeadacheFatigueOccasionalSkin rash on truckSwollen lymph glandsEye painWNV Severe DiseaseClinical FeaturesFeverGastrointestinal symptomsAtaxia and involuntary movementsOptic neuritisSeizuresWeaknessChange in mental statusMyelitisPolyradiculitisRash involving neck, trunk, arms or legs (occasional)WNV Severe Disease (cont)When CNS is affected symptoms indistinguishable from other similar viral syndromes

60%-70% with neuroinvasive WNV altered mental status or focal neurologic findings

Headache alone not useful indicator of neuroinvasive disease

25%-35% have meningitis w/o evidence of encephalitis

WNV Severe Disease (cont)West Nile Meningitis

Involves fever, headache and stiff neck

Elevated WBC in spinal fluid

Changes in consciousness not usually seen (if so, mild)

WNV Severe Disease (cont)West Nile Encephalitis

Most severe form of neuroinvasive WNV disease

Usually alteration of consciousnessMild with lethargyMay progress to confusion or coma

Limb paralysis/cranial nerve palsies possible

WNV Severe Disease (cont)West Nile Poliomyelitis

Flaccid paralysis associated with WNV infection

Less common than meningitis or encephalitis

Acute onset of asymmetric limb weakness or paralysis in absence of sensory loss

Pain can precede paralysis

Paralysis can occur in absence of common symptoms

WNV Severe Disease (cont)Common Lab Findings

Total white count mostly normal

Low Sodium (mostly with encephalitis)

CSF examinationNormal glucoseElevated proteinElevated WBC (mostly lymphocytes)

WNV Severe Disease (cont)Diagnostic TestsLab tests required for confirmationMost efficient detection of IgM antibody to WNVSerum collected within 8-14 days of illness onsetCSF collected within 8 days of illness onsetIgM does not cross blood-brain barrier (presence strongly suggests WNV)Vaccination or non-CNS infections - no CSF IgM(Yellow Fever, Dengue, Japanese Encephalitis)Virus culture Gold Standard (rarely positive except at autopsy)West Nile VirusClinical SuspicionDx based upon High Index Suspicion and Lab Tests

Age is greatest risk factorAdults 50 yrs + with onset of unexplained encephalitis or meningitis in late summer or early fall

Local human cases of WNV infection

Can occur in all ages and year-round transmission possible in southern states

West Nile Virus - TreatmentNo specific treatment

No vaccine

Supportive care for severe casesHospitalizationIV fluidsRespiratory supportPrevention of secondary infectionsWest Nile Virus - Prevention

West Nile Virus - PreventionVector Control

Insect Repellant

Protective Clothing

Avoid Exposure Dusk to Dawn

EducationWest Nile Virus Activity (10/2/12)

West Nile Virus Activity (10/2/12)Total Cases - 3969Non-Neuroinvasive1959 cases (OK 72 cases/ TX - 764)

Neuroinvasive2010 cases (OK 90 cases/ TX - 674) Deaths - 163OK -9TX - 54

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