WNV UW PHSemMOD

West Nile Virus: An Emerging Disease : West Nile Virus: An Emerging Disease Linda C. Glaser, DVM Wisconsin Division of Public Health


West Nile Virus -Background : West Nile Virus -Background First isolated in 1937 in Uganda First recorded human epidemics in Israel in the 1950s Since mid-1990s 10 human outbreaks in 7 counties since 1994 Increase in frequency of human outbreaks Increase in severity of human disease High avian death rates w/human outbreaks in Israel, US The New York 1999 strain of WNV most similar to an isolate from a domestic goose in Israel


West Nile Virus -Background : West Nile Virus -Background Birds are the primary hosts Most classes of vertebrates susceptible to infection - mammals, birds, reptiles, amphibians Humans are incidental hosts with typical infection causing mild flu-like symptoms High-titer viremia sufficient to transmit a virus is rare in species other than birds.


West Nile Virus - Mosquitoes : West Nile Virus - Mosquitoes 175 mosquito species found in the U.S. Over 50 species of mosquitoes in Wisconsin Not all of them bite people Only female mosquitoes seek blood meals Very few mosquitoes are infected with virus Typically <1% mosquitoes of any species found with virus


West Nile Virus - Transmission Cycle : West Nile Virus - Transmission Cycle Reservoir hosts Transmission Cycle


West Nile Virus - Worldwide Distribution : West Nile Virus - Worldwide Distribution


West Nile Virus – 1999 Distribution : West Nile Virus – 1999 Distribution


West Nile Virus - 1999 Distribution in the U.S. : West Nile Virus - 1999 Distribution in the U.S.


West Nile Virus - 2000 Distribution in the U.S. : West Nile Virus - 2000 Distribution in the U.S.


West Nile Virus - 2001 Distribution in the U.S. : West Nile Virus - 2001 Distribution in the U.S.


West Nile Virus - 2002 Distribution in the U.S. : West Nile Virus - 2002 Distribution in the U.S.


West Nile Virus : West Nile Virus


West Nile Virus In Wisconsin : West Nile Virus In Wisconsin


West Nile Virus In Wisconsin : West Nile Virus In Wisconsin WNV Dead Bird Surveillance Sensitive indicator of viral activity in the environment Monitor the spread of the virus Crudely estimates intensity of epizootic Does not predict human risk


West Nile Virus In Wisconsin : West Nile Virus In Wisconsin Data collection Recorded reports of sick and dead corvids (crow, raven, and blue jay) Report located to zip code for mapping Report identified a date found 5873 reports from 5/1-10/31/02 532 of 791 birds tested were positive (between 6/25/02 and 10/08/02)


West Nile Virus In Wisconsin : West Nile Virus In Wisconsin # Corvids Reported (N=5873) # Corvids Positive for WNV(N=532) 2002 Statewide Corvid Data


West Nile Virus In Wisconsin : West Nile Virus In Wisconsin # Corvids Positive (N=532) # Corvids Negative (N=257) 2002 Statewide Corvid Data


West Nile Virus In Wisconsin : West Nile Virus In Wisconsin WNV Dead Bird Surveillance Data used for mapping 5873 reports from 5/1-10/31/02 Report mapped with a randomly assigned dot within the zip code location Created time sequence using the date found


West Nile Virus In Wisconsin : West Nile Virus In Wisconsin Corvids Reported Sick/Dead in 2002


West Nile Virus In Wisconsin : West Nile Virus In Wisconsin 52 people with illness from WNV in 2002 (Age range: 20-93 yo) 3 fatalities Date of illness onset from 7/13-10/20/02 (N=48) 29 of 47 people were hospitalized 16 of 42 people had severe illness (neurological involvement)


West Nile Virus In Wisconsin : West Nile Virus In Wisconsin


West Nile Virus In Wisconsin : West Nile Virus In Wisconsin # Corvids Reported (N=5873) # Humans Positive for WNV(N=52) 2002 Statewide Corvid Data and Human Data


West Nile Virus - Human Infections 2002 Epidemic in the U.S. : West Nile Virus - Human Infections 2002 Epidemic in the U.S.


West Nile Virus - Human Infections 2002 Epidemic in the U.S. : West Nile Virus - Human Infections 2002 Epidemic in the U.S. Western hemisphere’s largest arboviral ME epidemic 2,741 WNME cases 1,267 WNF / unspecified 263 deaths 39 states & D.C Largest WNME epidemic EVER New clinical syndromes Five new transmission modes * As of 2/5/2003 West Nile virus: New modes of transmission Dr. Anthony Marfin, M.D, MPH 4th WNV Nat’l Conference


Slide25 : ~80% Asymptomatic ~20% “West Nile Fever” <1% CNS disease ~10% fatal (<0.1% of total infections) WNV Human Infection “Iceberg” 1 CNS disease case = ~150 total infections Very crude estimates Emerging Clinical Syndromes of West Nile Virus Infection Dr. J. Sevjar, M.D 4th WNV Nat’l Conference


West Nile Virus - Human Infections : West Nile Virus - Human Infections Incubation period of 2-15 days Most illness is “West Nile Fever” self-limited headache with fever rash, lymphadenopathy nausea, vomiting Rarely pancreatitis, hepatitis, myocarditis


West Nile Virus - Human Infections : West Nile Virus - Human Infections Severe neurologic illness categories Meningitis - fever, neck stiffness, CSF pleocytosis Encephalitis - altered mental status ‘Meningoencephalitis’ Acute flaccid paralysis


West Nile Virus - Human Infections Clinical Investigations in 2002 : West Nile Virus - Human Infections Clinical Investigations in 2002 Prospective clinical case series Detailed serial neurologic exams 16 patients identified WNV Fever Study Detailed neurodiagnostic studies on large numbers of patients House-to-house serosurvey Emerging Clinical Syndromes of West Nile Virus Infection Dr. J. Sevjar, M.D, 4th WNV Nat’l Conference


West Nile Virus - Human InfectionsClinical Syndromes-The Scope of Illness : West Nile Virus - Human Infections Clinical Syndromes-The Scope of Illness West Nile fever Emerging clinical syndromes Movement disorders Parkinsonism Flaccid paralysis Rhabdomyolysis Outcomes / prognosis Future directions Emerging Clinical Syndromes of West Nile Virus Infection Dr. J. Sevjar, M.D, 4th WNV Nat’l Conference


West Nile Virus-Human InfectionsWest Nile Fever : West Nile Virus-Human Infections West Nile Fever Felt to represent the majority of symptomatic infections Subacute progression to severe CNS disease unlikely Development of meningitis / encephalitis / paralysis within 24-48 hours of fever onset No subsequent hospitalization among fever outpatients Increased detection—fewer cases truly asymptomatic?? Emerging Clinical Syndromes of West Nile Virus Infection Dr. J. Sevjar, M.D, 4th WNV Nat’l Conference


West Nile Virus-Human InfectionsClinical Outcomes Data : West Nile Virus-Human Infections Clinical Outcomes Data Current data limited 10% fatality rate with CNS disease Long term outcomes in NYC patients >50% w/continued impairment at 1 year 37% considered fully recovered Emerging Clinical Syndromes of West Nile Virus Infection Dr. J. Sevjar, M.D, 4th WNV Nat’l Conference


West Nile Virus-Human InfectionsClinical Outcomes Data : West Nile Virus-Human Infections Clinical Outcomes Data Short-term prospective data No deaths Most patients (14/16; 88%) eventually went home Follow-up Persistent / chronic headache Concentration, memory difficulties Overwhelming fatigue Persistence of tremor, parkinsonism Paralysis - no short-term improvement Emerging Clinical Syndromes of West Nile Virus Infection Dr. J. Sevjar, M.D, 4th WNV Nat’l Conference


West Nile Virus-Human InfectionsModes of Transmission : West Nile Virus-Human Infections Modes of Transmission Transplantation Transfusion Breastfeeding Transplacental transmission Occupational exposure


West Nile Virus-Human InfectionsTransmission by transplantation (TPX) : West Nile Virus-Human Infections Transmission by transplantation (TPX) Except for HCV and HGV, NO well-documented reports of flavivirus transmission via TPX Nov ‘94: Puerto Rico dengue outbreak – 6 yr old with probable transmission due to bone marrow TPX (Rigau et al AJTMH 2001) West Nile virus: New modes of transmission Dr. Anthony Marfin, M.D, MPH, 4th WNV Nat’l Conference


West Nile Virus-Human InfectionsCase of TPX Transmission : West Nile Virus-Human Infections Case of TPX Transmission Organ Donor Blood components 63 donors Organ Donor 36 hours F/U: 1 seroconverting donor; Stored plasma –WNV PCR-positive West Nile virus: New modes of transmission Dr. Anthony Marfin, M.D, MPH, 4th WNV Nat’l Conference


West Nile Virus-Human InfectionsTPX Associated Transmission : West Nile Virus-Human Infections TPX Associated Transmission TPX-associated transmission confirmed High attack rate: 4/4 organ recipients ill 3/4 develop encephalitis Large viral load, immunosuppressive drugs Unusual clinical findings: Symptoms 7-17 days post-TPX Minimal CSF pleocytosis observed Organ donor’s infection from infectious blood unit West Nile virus: New modes of transmission Dr. Anthony Marfin, M.D, MPH 4th WNV Nat’l Conference