westnilevirus 071205

West Nile VirusJuly 12, 2005: 

West Nile Virus July 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

WNV is an Arthropod-Borne virus: 

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

Slide3: 

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

WNV Prevention Based on Transmission: 

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

Repellent Guidance : 

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

Transmission: 

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)

Screening of Blood Supply: 

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

Presumptively Viremic Blood Donors, 2004: 

Presumptively Viremic Blood Donors, 2004

Presumptively Viremic Blood Donors, 2005: 

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

WNV and Pregnancy : 

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?

WNV and Pregnancy: 

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

Slide12: 

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

WNV Fever: 

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

WNV Meningitis: 

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

WNV Encephalitis: 

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

WNV-Associated Flaccid Paralysis: 

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

Risk for Severe Disease : 

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

Diagnosis of WNV Infection: 

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

Reporting: 

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

WNV Treatment: 

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

WNV Outcomes: 

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

WNND County Level Incidence per Million, United States, 2004: 

WNND County Level Incidence per Million, United States, 2004

2004, WNV Activity: 

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

2005 WNV Activity, as of 5 July 2005: 

2005 WNV Activity, as of 5 July 2005

Info Online: 

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

Registry for Women Infected with WNV while Pregnant: 

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