WEST NILE VIRUS (WNV) A Growing Concern

1. WEST NILE VIRUS (WNV)A Growing Concern George A. Fisher, PA-C, MPH, DFAAPA October 25, 2012

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

3. Origins • 1937 - First isolated in the West Nile District, Uganda • 1950’s – Presence described in Egypt • 1957 – Severe human encephalitis in elderly (Israel) • 1960’s – Equine disease 1st noted in Egypt and France • 1999 – First appearance of WNV in North America in humans and horses

4. West Nile Virus (Arbovirus)

5. West Nile Virus • Single- Stranded RNA virus (Flavivirus genus) • Arbovirus (Arthopod-borne) • Member of Japanese encephalitis virus complex • Japanese Encephalitis • St Louis Encephalitis • Murray Valley Encephalitis • Since 1999 very few genetic changes in US strains (versus influenza strains)

6. West Nile Virus - Transmission

7. West Nile Virus - Transmission • Alternate Routes (very small proportion of cases) • Transplanted organs • Blood transfusions • Breastmilk (one probable case) • Transplacental • Occupational Exposure (two lab workers)

8. WNV- Culex species

9. Distribution of Outbreaks Human Encephalitis • 1994 – Algeria • 1996-97 – Romania • 1997 – Czech Republic • 1998 – Democratic Republic of Congo • 1999 – Russia • 1999-2003 – United States • 2000 - Israel

10. Distribution of Outbreaks Equine Disease • 1996 – Morocco • 1998 – Italy • 1999-2001 – United States • 2000 - France

11. Distribution of Outbreaks • Bird 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)

12. WNV – Human Disease • Mild Disease • West Nile Fever • Severe Disease • West Nile Meningitis • West Nile Encephalitis • West Nile Poliomyelitis

13. West Nile Fever • Incubation Period • 2 to 14 days (documented longer in immunosuppressed population) • Clinical Features (only 20% develop symptoms) Primary • Fever • Headache • Fatigue Occasional • Skin rash on truck • Swollen lymph glands • Eye pain

14. WNV – Severe Disease • Clinical Features • Fever • Gastrointestinal symptoms • Ataxia and involuntary movements • Optic neuritis • Seizures • Weakness • Change in mental status • Myelitis • Polyradiculitis • Rash involving neck, trunk, arms or legs (occasional)

15. 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

16. 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)

17. WNV – Severe Disease (cont) • West Nile Encephalitis • Most severe form of neuroinvasive WNV disease • Usually alteration of consciousness • Mild with lethargy • May progress to confusion or coma • Limb paralysis/cranial nerve palsies possible

18. 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

19. WNV – Severe Disease (cont) • Common Lab Findings • Total white count mostly normal • Low Sodium (mostly with encephalitis) • CSF examination • Normal glucose • Elevated protein • Elevated WBC (mostly lymphocytes)

20. WNV – Severe Disease (cont) • Diagnostic Tests • Lab tests required for confirmation • Most efficient – detection of IgM antibody to WNV • Serum – collected within 8-14 days of illness onset • CSF – collected within 8 days of illness onset • IgM – 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)

21. West Nile Virus • Clinical Suspicion • Dx based upon High Index Suspicion and Lab Tests • Age is greatest risk factor • Adults 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

22. West Nile Virus - Treatment • No specific treatment • No vaccine • Supportive care for severe cases • Hospitalization • IV fluids • Respiratory support • Prevention of secondary infections

23. West Nile Virus - Prevention

24. West Nile Virus - Prevention • Vector Control • Insect Repellant • Protective Clothing • Avoid Exposure – Dusk to Dawn • Education

25. West Nile Virus Activity (10/2/12)

26. West Nile Virus Activity (10/2/12) • Total Cases - 3969 • Non-Neuroinvasive • 1959 cases (OK – 72 cases/ TX - 764) • Neuroinvasive • 2010 cases (OK – 90 cases/ TX - 674) • Deaths - 163 • OK -9 • TX - 54

27. ? Questions ?