west nile virus (wnv) a growing concern
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WEST NILE VIRUS (WNV) A Growing Concern . George A. Fisher, PA-C, MPH, DFAAPA October 25, 2012. West Nile Virus. Objectives Be familiar with the prevalence of the West Nile Virus Know the etiology, signs and symptoms, and treatment for infections from West Nile Virus - PowerPoint PPT PresentationTRANSCRIPT
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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