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West Nile Virus: Surveillance and Clinical Issues

This article discusses the surveillance and clinical aspects of West Nile Virus (WNV), including symptoms, diagnosis, and treatment options. It also provides information on the region where the virus originated. Stay informed and learn how to protect yourself from WNV.

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West Nile Virus: Surveillance and Clinical Issues

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  1. West Nile Virus: Surveillance and Clinical Issues Anne Kjemtrup, DVM, MPVM, Ph.D. California Department of Public Health Vector-Borne Disease Section 1

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  3. 3/21 6/27 6/20 1/29 4/4 Sequence of WNV detection events in California relative to human caseonset, 2008 Number of human cases Disease Week of Onset Jan Feb Mar Jun Jul Sep Oct Nov Dec Apr May Aug 3

  4. ~10% of WNND are fatal (<0.1% of total infections) <1% WNND ~20% West Nile fever ~80% Asymptomatic The Clinical “Pyramid Picture” 4

  5. West Nile fever • Typical clinical manifestations • Fever • Headache • Fatigue • Muscle weakness • Muscle aches • Skin rash on trunk of body • Anorexia • Duration of illness=3 – 6 days • Outcome: in general, excellent w/o specific treatment 5

  6. 6 *Watson JT et al. Ann Intern Med 2004; 141:360-5

  7. West Nile Neuroinvasive Disease • Aseptic Meningitis (25%-35% WNND cases) • Fever, headache, malaise, muscle weakness • Nausea, vomiting, stiff neck, myalgia, cranial nerve palsies • Outcome generally good • Encephalitis (60% - 70% WNND cases) • Alternation of consciousness (lethargy  coma), tremors, weakness, brainstem/cranial nerve deficits, cerebellar signs/symptoms • Outcome variable. Fatality-case ratio up to 15%; increases with advanced age. Potential of long-term neurologic deficits in some patients. • WNV “Poliomyelitis”- a flaccid paralysis syndrome (uncommon). • Acute onset of asymmetric limb weakness or paralysis in absence of sensory loss • Can occur in the absence of fever, headache, or other WNV-associated signs. 7

  8. Preliminary Univariate Analysis (2006):Risk Factors for Developing WNND vs. WN Fever 8

  9. WNV Outcome Picture • Risk factors for severe disease include increasing age, immunosuppression, diabetes, and hypertension. • Though risk of WNV infection higher in children than adults, risk of WNND in children lower than adults. • Most WNF patients recover in first few months. For some, problems may linger (subclinical encephalitis? Other risk factors?). (Encephalitis Outcome Study Shilpa Gavali-Jani, VRDL; Carson et al., CID 2006; Haaland et al EID 2006) 9

  10. “We’re pretty sure it’s the West Nile virus...” Diagnosis 10

  11. West Nile virus 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 11

  12. West Nile virus Laboratory Testing • IgM antibody-capture ELISA for serum collected within 8-14 days of illness onset or CSF collected within 8 days of illness onset • IgM in CSF strong suggests CNS infection since IgM does not cross blood-brain barrier. • Plaque-reduction neutralization test (PRNT) used to distinguish false-positive results or cross reactivity with other arboviruses 12

  13. West Nile virus 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! 13

  14. Treatment • Supportive Care • Experimental: Clinical trial of interferon for meningoencephalitis patients underway. 14

  15. For More Information:www.westnile.ca.gov 15

  16. Where it all began… West Nile Region of Uganda Mt. Luku Islandmountain Murchison Falls 16 • www.game-reserve.com/uganda_murchison_falls.html • www.min.uni-kiel.de/.../ugandaweb/wnile.html

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