West Nile Virus July 12, 2005

1. West Nile VirusJuly 12, 2005 Theresa Smith, MD Emily Zielinski-Gutierrez, DrPH Division of Vector Borne Infectious Diseases (DVBID) National Center for Infectious Diseases Centers for Disease Control and Prevention Fort Collins, Colorado

2. WNV is an Arthropod-Borne virus • First discovered in 1937 in the West Nile district of Uganda • Until 1999 only found in Asia, Southern Europe, Africa • Flavivirus, in the Japanese Encephalitis Antigenic Complex –similar family to Yellow Fever, St. Louis encephalitis virus • Transmitted by mosquitoes

3. WNV: Basic Transmission Cycle Most important cycle is from mosquito to bird to mosquito “Incidental” infections: unlikely amplifying hosts Amplifying hosts

4. WNV Prevention Based on Transmission • Personal-emphasize at times of high mosquito activity (dawn/dusk) or stay indoors • Use mosquito repellent • Wear long sleeves, pants • Household • Use/ fix screens • Air-conditioning • Empty standing water • Community / environmental • Empty standing water

5. Repellent Guidance • Skin • DEET still “gold standard” • Both new additions good for shorter term protection • Picaridin • Roughly equivalent to DEET at same concentration • Only a 7% product currently sold in US • Oil of lemon eucalyptus • Plant based • 30% product similar to low concentration DEET • Not for kids <3 years old • Clothing • Permethrin

6. Transmission • The most common route of infection is bite of infectious mosquito • 2002 revealed other modes • Blood Transfusion • Organ Transplantation • Intrauterine • Percutaneous exposure (occ. exposure) • Breastmilk (probable)

7. Screening of Blood Supply • As of July 2003, all blood donated in US is screened for WNV using nucleic acid amplification testing (NAT) • Platform under IND • Use of NAT continues to be refined • Transfusion-associated risk very, very low • In 2004, 224 PVDs identified • One transfusion-associated transmission associated with a change in use of NAT

8. Presumptively Viremic Blood Donors, 2004

9. Presumptively Viremic Blood Donors, 2005 As of July 5, 2005

10. WNV and Pregnancy • One confirmed intrauterine WNV infection (2002) • Zero cases of WNV intrauterine transmission detected in 79 pregnancies (2003-4) • Three cases of early post-natal WNV infection • Transplacentally transmitted?

11. WNV and Pregnancy • Nine major birth defects were detected (12 percent of live births) • Chance occurrences • Phenotypic inconsistency (except microcephaly) • Maternal WNV infection often followed expected timing of defect development • Registry for pregnant women with WNV

12. WNV Human Infection “Iceberg” For every case of illness involving the brain or spinal cord, ~150 total infections ~10% of CNS ds are fatal (<0.1% of total infections) <1% CNS disease ~20% “West Nile Fever” ~80% Asymptomatic

13. WNV Fever • Most who get sick from WNV infection have WNV fever • Time from mosquito bite to illness averages 3-5 days • Fever, chills, headache, fatigue can be severe • Nausea, vomiting • Rash, usually not itchy, lasting a few days, mainly on chest, back, abdomen, and/or arms • Usually better within a week, though persistent headache, fatigue common -- reports of weeks, even longer among otherwise healthy persons

14. WNV Meningitis • Fever, headache, meningismus, photosensitivity • White blood cells in the cerebrospinal fluid • Headache may be quite severe • Most people improve, though persistent headache, fatigue common

15. WNV Encephalitis • Severity ranges from mild confusion to coma and death • Other symptoms • Tremor • Myoclonus • Dizziness

16. WNV-Associated Flaccid Paralysis • Recognized more frequently in the last 2 years • Affects relatively healthy young people • May not have fever or headache before paralysis • Clinical hallmarks: • Onset early in infection • Weakness can often be in only one limb • Absence of numbness; pain sometimes present

17. Risk for Severe Disease • Persons over 50 at higher risk • Solid organ transplant recipients

18. Diagnosis of WNV Infection • Suspect in meningitis, encephalitis, or flaccid paralysis from summer through fall, or December in the South • Consider other arboviral diseases such as St. Louis encephalitis • Local WNV enzootic activity or other human cases should raise suspicion • Recent travel history also important • State labs can help with diagnostic testing of serum or CSF for WNV IgM and/or IgG

19. Reporting • Reporting procedures vary by state – Check with state coordinators/state websites • All human WNV illness is reportable as of 2004

20. WNV Treatment • No specific treatment for WNV disease • 3 IRB-approved, randomized, double-blinded, placebo-controlled clinical trials available

21. WNV Outcomes • Neuroinvasive disease • 10-20% with severe disease die • Fatalities primarily among elderly, immunosuppressed • WNV flaccid paralysis • Some people with almost complete recovery; others with continued weakness • Those with less severe initial weakness tend to have a better prognosis

22. Incidence per million .01-9.99 Any WNV Activity 10-99.99 >=100 WNND County Level Incidence per Million, United States, 2004

23. 2004, WNV Activity (available : http://www.cdc.gov/ncidod/dvbid/westnile/surv&control04Maps.htm)

24. 2005 WNV Activity, as of 5 July 2005

25. Info Online • West Nile Virus: Information and Guidance for Clinicians • http://www.cdc.gov/ncidod/dvbid/westnile/clinicians/ • http://www.cdc.gov/ncidod/dvbid/westnile/clinicalTrials.htm • Diagnosis section http://www.cdc.gov/ncidod/dvbid/westnile/resources/fact_sheet_clinician.htm

26. Registry for Women Infected with WNV while Pregnant • Interim Guidelines for the evaluation of infants born to women infected with WNV during pregnancy. See: http://www.cdc.gov/ncidod/dvbid/westnile/DuringPregnancy/WNV_duringPregnancy.htm