westNile

West Nile Virus InfectionAn Update: 

West Nile Virus Infection An Update Shobita Rajagopalan, M.D. Associate Professor Division of Infectious Diseases King-Drew Medical Center

Topic Content: 

Topic Content Background and Epidemiology The Case Count Ecology Virology Clinical Characteristics Pathogenesis Diagnosis and Laboratory Findings Clinical Outcome and Treatment Reporting and the Role of Public Health Prevention

Slide3: 

West Nile Fever: Background & Epidemiology First isolated in West Nile district, Uganda, 1937 Commonly found in humans and birds & other vertebrates in Africa, Eastern Europe, West Asia, and the Middle East, but has not previously been documented in the Western Hemisphere Basic transmission cycle involves mosquitoes feeding on birds infected with the West Nile virus Infected mosquitoes then transmit West Nile virus to humans and animals when taking a blood meal

Slide4: 

West Nile Virus Transmission Cycle AMPLIFICATION

West Nile Outbreaks: 

West Nile Outbreaks Israel – 1951 to 1954, 1957, 2000 France – 1962, 2000 South Africa - 1974 Romania - 1996 Italy - 1998 Russia - 1999 United States – 1999 to 2002

West Nile Virus in the US Some Possible Pathways of Introduction: 

West Nile Virus in the US Some Possible Pathways of Introduction Infected human host Human-transported vertebrate host Legal Illegal Human-transported vector(s) Storm-transported vertebrate host (bird) Intentional introduction (terrorist event)

First US Cases in Staten Island: 

First US Cases in Staten Island Staten Island Ferry Tug boat

Kill Van Kull: The Staten Island Landfill: 

Kill Van Kull: The Staten Island Landfill Truck dumping waste Last truck with seagulls

Staten Island: 

Staten Island VZ Bridge Horse reservoir

Location where SI cases reported(left) and landfill (right): 

Location where SI cases reported (left) and landfill (right)

Date of Symptom Onset, West Nile VirusUnited States, 1999-2001: 

Date of Symptom Onset, West Nile Virus United States, 1999-2001

Slide13: 

WNV Case-Patient Demographics & Mortality United States, 1999-2001

West Nile Virus in the United States: 

West Nile Virus in the United States Monitor geographic and temporal spread Develop more effective strategies for surveillance, prevention and control Define regional distribution and incidence of other arboviral diseases Provide current national and regional information National Surveillance Plan

West Nile Virus Update Archive: 

West Nile Virus Update Archive For the current case count please visit: http://www.cdc.gov/od/oc/media/wncount.htm

Slide19: 

Ecology West Nile virus is maintained in an enzootic cycle involving culicine mosquitoes and birds Mosquitoes Culex pipiens, restuans, and quinquefasciatus Birds (111 bird species have been reported to CDC's West Nile Virus avian mortality database from 1999-present) N. American corvids most common e.g., American crows, ravens, jays & other crows

Ecology continued: 

Ecology continued Culex mosquito Dead raven C. quinquefasciatus

Slide21: 

AMPLIFICATION West Nile Virus Transmission Cycle

Risk of West Nile Virus Transmission Through Blood Transfusion: 

Risk of West Nile Virus Transmission Through Blood Transfusion Concern: most WNV infections have no or only mild symptoms, and transient viremia occurs after infection Transfusion-transmission of WNV or other related flaviviruses not reported, but plausible Mathematical modeling: estimated risk of transfusion-transmission was 2 in 10,000 during NYC outbreak (Transfusion, Aug 2002) WNV should be considered in persons who develop unexplained fever, meningitis, or encephalitis after transfusion

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Virology Single stranded RNA virus Family: Flaviviridae Genus: Flavivirus Only lineage 1 has been definitely associated with human disease E-glycoprotein: viral hemagglutinin mediates virus-host cell binding elicits virus neutralizing antibodies

Slide24: 

Flaviviruses (e.g., Yellow fever, dengue, DHF, JE. SLE, tick-borne E viruses) About 70 members, half of which are principally associated with arthropod-borne human disease Enveloped, spherical virion, 40 - 50 nm Two surface proteins: E (envelop) & M (membrane) (prM: premembrane M protein precursor) Icosahedral capsid, 25 - 30 nm ssRNA genome, linear, positive polarity, 11 kb

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Lineage 1 has been definitely associated with human disease

Members of Japanese encephalitis virus serocomplex: 

West Nile virus Japanese encephalitis St. Louis encephalitis Murray valley encephalitis (Australian sub type) Kunjin virus (Australian subtype) Members of Japanese encephalitis virus serocomplex

The Japanese Encephalitis Serocomplexof the Family Flaviviridae: 

The Japanese Encephalitis Serocomplex of the Family Flaviviridae

Slide30: 

Electron microscopic view of West Nile virus isolated from brain tissue from a crow found in New York. Magnification:  65,625x

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Flaviviral Encephalitis Variable and potentially lengthy incubation period of 4 to 21 days (usually 1 week) reflects the interval for viral replication locally and in peripheral sites, with a subsequent brief viremia before the virus invades the CNS Virus rarely can be recovered from blood, within 1 week after the onset of illness & before onset of neurologic Sx The vast majority of infections that are asymptomatic, approximately 300 for each symptomatic case, is striking & remarkably consistent among SLE, JE, & WNE

Causes of Acute Encephalomyelitis: 

Causes of Acute Encephalomyelitis Viral Togaviridae EEE. WEE. VEE Flaviviridae WN, SLE, JE, MV. De Bunyaviridae LaCrosse, Rift Valley, Toscana Paramyxoviridae Measles, mumps Arenaviridae LCM, Lassa, Junin, Machupo Retroviridae Lentivirus: HIV Viral contd Picornaviridae Enteroviruses (polio, coxsackie, hep A) Reoviridae Colorado tick fever Rhabdoviridae Rabies, lyssavirus Filoviridae Ebola and Marburg Herpesviridae HSV, VZV, EBV, CMV, HHV6, Herpes B virus Adenoviridae Post infection: toga, poxorthomyxo, paramyxo, herpes

Non-viral causes of Acute E: 

Non-viral causes of Acute E RMSF Typhus Ehrlichia Q fever Brucella Bartonella Listeria Chlamydia Mycoplasma Legionella SBE Spirochetes Borrelia Leptospira Higher bacteria Mycobacteria Fungi Parasites Non infectious causes Vasculitides, malignancies, drug reactions etc

Slide34: 

enteroviruses, mumpsviruses, herpesviruses & tick borne diseases ‘

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Clinical description indistinguishable from similar syndromes caused by other viruses - asymptomatic illness of variable severity central nervous system (CNS) involvement febrile headache to aseptic meningitis to encephalitis Arboviral encephalitis

Arboviral encephalitisCNS manifestations: 

Arboviral encephalitis CNS manifestations Fever Headache Altered mental status Confusion to coma with or without paresis or paralysis Cranial nerve palsies Sensory deficits Abnormal reflexes Generalized convulsions Abnormal movements

Slide37: 

WNF: Classical Clinical Description Incubation period usually 5 (3) to 15 days Asymptomatic or mild dengue-like illness in ~20%: “West Nile Fever” Fever, lymphadenopathy, headache, abdominal pain, vomiting, rash, conjunctivitis 1 in 150 develop meningoencephalitis CNS involvement & death in few cases Advanced age primary risk factor for severe neurological disease and death

Slide38: 

Petersen et al., Ann Int Med 2002;137:173-9

Symptoms of Hospitalized Patients withWest Nile Virus, New York City, 1999: 

Symptoms of Hospitalized Patients with West Nile Virus, New York City, 1999 2% Lymphadenopathy 19% Rash 27% Diarrhea 46% Change in mental status 47% Headache 51% Vomiting 53% Nausea 56% Weakness 90% Fever

Neurological Presentations of West Nile Virus Infection: 

Neurological Presentations of West Nile Virus Infection New York City 1999 Encephalitis/meningoencephalitis 62% Meningitis 32% Complete flaccid paralysis 10% Confused with Guillain-Barre syndrome EMG and nerve conduction velocity studies indicating both axonal and demyelinating lesions, with axonal lesions most prominent Previous series Ataxia, extrapyramidal signs, cranial nerve abnormalities, myelitis, optic neuritis, seizures

Neurological Presentations of West Nile Virus Infection: 

Neurological Presentations of West Nile Virus Infection Preliminary data 2002 Complaints of weakness out of proportion to evidence on physical exam Myoclonus nearly a universal finding Some patients have Parkinsonian-like signs

Pathogenesis: 

Pathogenesis Subclinical infection presumably reflects the peripheral clearance of virus before neuroinvasion Virus enters the CNS from the blood by growing through vascular endothelial cells to the parenchymal side or, alternatively, through the olfactory epithelium Within the brain, virions spread from cell to cell

Pathogenesis: 

Pathogenesis Pathologic changes : meningeal congestion and inflammation brain edema widespread encephalitis with a predilection for the hippocampus and temporal cortex, thalamus, substantia nigra, cerebellum, periventricular areas of the brain stem, & anterior spinal cord

Diagnosis: 

Diagnosis Clinical and epidemiological clues Isolation of the virus Serological assays

Basic Laboratory Findings from WNV Outbreaks in New York and Israel: 

Basic Laboratory Findings from WNV Outbreaks in New York and Israel Total leukocyte count normal or slightly elevated Hyponatremia rarely in patients with encephalitis CSF Leukocytes 0 - 1782 cells/mm3, mostly lymphocytes Protein universally elevated 51 - 899 mg/dL Glucose normal CT brain: no evidence of acute disease MRI in 1/3 showed enhancement of leptomeninges, periventricular areas, or both

Slide46: 

Serum, CSF Mosquito pools, Tissues Serological Assays Virus Detection Assays IgM ELISA IgG ELISA Plaque Reduction NT Comp Fix Hem. Inhibition Indirect FA Virus isolation (cells, mice) Immuno Fluorescence Assay TaqMan RT-PCR Ag-capture ELISA Dipsticks RT-PCR / sequencing Diagnostic Assays for Arboviruses

WN Virus Antigen Detection Assays: 

WN Virus Antigen Detection Assays Virus Isolation Antigen Detection IFA – Mabs Ag – Capture Dipsticks Immunohistochemistry

Sensitivity of Virus Assays: 

Sensitivity of Virus Assays TaqMan/NASBA > Isolation> Ag Capture

Slide49: 

e e s s Antiviral MAb to well Unknown virus sample Antiviral MAb conjugate Substrate addition Antigen Capture Assay

VecTest™ WNV/SLE Dipstick assay: 

VecTest™ WNV/SLE Dipstick assay Procedure: VecTest strip 250 l mosquito pool suspension 15 min

Slide51: 

RNA Extraction from Serum, CSF, Tissue, & Mosquito Pools Standard RT-PCR TaqMan RT-PCR NASBA SYBR Green RT-PCR Molecular Amplification Assays

Serological Tests: 

Because closely related arboviruses exhibit serologic cross-reactivity, positive results of serologic test using antigens from a single arbovirus can be misleading  Cross-neutralization tests using an appropriate battery of closely related viruses may essential Determine that antibodies detected against St. Louis encephalitis are not the result of an infection with West Nile (or dengue) virus, or vice versa, in areas where both of these viruses occur Serological Tests

Slide53: 

Information Needed for Serological Testing and Interpretation Date of onset of disease Dates of sample collection Travel history Vaccination history Clinical encephalitis

Differential diagnosis: 

Differential diagnosis

Slide55: 

Patient Days IgM (WN) IgG (SLE) WN SLE DEN2 JE CSF 8 26.91 1.78 nd nd nd nd S1 9 9.1 4.16 160 20 <10 10 S2 34 6.7 4.62 1280 20 <10 20 Positive Control n.a. 9 6.5 >5120 2560 2560 320 Serological Analysis of A WN Case

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Laboratory criteria for diagnosis Isolation of virus or demonstration of spiral viral antigen or genomic sequences in tissue, blood, cerebrospinal fluid (CSF), or other body fluid, or Fourfold or greater change in virus-specific serum antibody titer or -Virus-specific immunoglobulin M (IgM) antibodies demonstrated in CSF by antibody-capture enzyme immunoassay (EIA), or -Virus-specific IgM antibodies demonstrated in serum by antibody-capture EIA and confirmed by demonstration of virus-specific serum immunoglobulin G (IgG) antibodies in the same or a later specimen by another serologic assay (e.g., neutralization or hemagglutination inhibition)

Slide57: 

Long Term WN virus IgM activity in human serum NYCDOH-CDC collaborative study N=28

Slide58: 

Petersen et. al Ann Int Med 2002 137:173-9

Slide59: 

Criteria for confirmation of West Nile encephalitis Febrile illness with neurologic manifestations plus at least one of the following: Isolation of West Nile virus from tissue, blood, CSF, or other body fluid Demonstration of West Nile viral antigen or genomic sequences in tissue, blood, CSF, or other body fluid Demonstration of West Nile virus IgM antibody in an acute CSF sample using MAC-ELISA Demonstration of fourfold change in PRNT antibody titer to West Nile virus in paired, appropriately timed acute and convalescent serum samples Demonstration of both West Nile virus–specific IgM (by MAC-ELISA) & IgG (by IgG ELISA or HI antibody titer; confirm by PRNT) in a single serum sample

Treatment: 

Treatment Supportive treatment About 25% require ICU care; 10% mechanical ventilation Ribavirin and interferon-a2b In-vitro activity in high doses One reported comatose patient did not improve Worse outcome with ribavirin in open-label trial in Israel – unclear patient selection

Slide61: 

Clinical Outcome Case fatality: 4% in Romania (1996) 12% in New York (1999) 14% in Israel (2000) 5% in US (2002) Risk factor : advance age, >70 year old Sequelae/morbidity (New York cases): fatigue (67%) memory loss (50%) difficulty walking (49%) muscle weakness (44%) depression (38%)

Outcome of West Nile Virus Infection among Hospitalized Patients: 

Outcome of West Nile Virus Infection among Hospitalized Patients At discharge (NY and NJ, 2000) More than half did not return to functional level Only one-third fully ambulatory At one year (NYC 1999 patients) Fatigue 67%, memory loss 50%, difficulty walking 49%, muscle weakness 44%, depression 38%

Predictors of Death among West Nile Virus-Infected Patients: 

Predictors of Death among West Nile Virus-Infected Patients Change in level of consciousness Encephalitis with severe muscle weakness Advanced age Possibly diabetes mellitus or immunosuppression

Partnerships for West Nile Virus in the United States: 

Partnerships for West Nile Virus in the United States Centers for Disease Control and Prevention U.S. Department of Agriculture U.S. Geological Survey Department of Defense Environmental Protection Agency State and Local Health Departments State and Local Veterinarians State and Local Wildlife Biologists

West Nile Virus – Human Cases: 

State Response Heightened Surveillance Public Information Medical Provider Information Mosquito Control West Nile Virus – Human Cases

State Response: 

PREVENTION State Response West Nile Virus – Human Cases

PREVENTION: 

West Nile Virus – Human Cases MosquitoControl Personal Protection PREVENTION

West Nile Virus Surveillance: 

Dead Bird Reports Dead Bird Testing Live Bird Testing Mosquito Testing Equine Cases Human Cases West Nile Virus Surveillance

Culex mosquito laying eggs : 

Culex mosquito laying eggs

Mosquito Habitat Elimination: 

Mosquito Control Habitat Elimination Adulticiding Larviciding Mosquito Habitat Elimination

Slide73: 

LOS ANGELES –The LAC DHS has received confirmation of the first case of West Nile virus infection in California. Laboratory test results indicate that the young adult woman whose infection had been considered “probable” was indeed infected with the virus. She has fully recovered. The tests were conducted at the University of California, Davis Arbovirus Research Laboratory, which is the state reference laboratory. The Centers for Disease Control and Prevention concur that this is a confirmed case. “We assume that the woman was bitten by a mosquito, the typical way in which a person is exposed to the virus,” said Jonathan Fielding, M.D., M.P.H., Public Health Director and County Health Officer. “However, mosquito surveillance units in Los Angeles and throughout the state have not detected any West Nile virus activity.” A second individual, a Texas resident, is hospitalized in the county with encephalitis probably due to infection with the virus, but health officials are confident that, if this is confirmed to be West Nile, he acquired the virus in Texas. The patient was visiting in the county and became ill the day after arriving in Los Angeles. Confirmed test results for this case will not be available for at least another week. There is only one other suspect case being followed by the county health department, with the results “indeterminate” at this time. COUNTY OF LOS ANGLES SEPTEMBER 12TH 2002 DEPARTMENT OF HEALTH SERVICES OFFICE OF COMMUNICATIONS 241 N. Figueroa Street, Room 348 * Los Angeles, CA 90012 Tel: (213) 240-8144 * Fax: (213) 481-1406 www.ladhs.org

The Message for the Clinicians: 

The Message for the Clinicians Any patient presenting with unexplained headache, weakness, fever, neurological symptoms or signs c/w meningitis, encephalitis or meningoencephalitis during the months of July through October requires a work up i.e., serological and CSF evaluation for infection with the West Nile Virus with involvement of local Public Health authorities in suspect cases

WNF Information: 

WNF Information http://www,cdc.gov http://www.dhs.co.la.us