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Information about wnv062904

Published on October 21, 2007

Author: Lucianna

Source: authorstream.com

West Nile Virus:  West Nile Virus Emily Zielinski-Gutierrez, DrPH Lisa Lundgren, RN, MSN, FNP-C Division of Vector Borne Infectious Diseases (DVBID) National Center for Infectious Diseases Centers for Disease Control and Prevention Fort Collins, Colorado West Nile Virus (WNV) before 1996:  West Nile Virus (WNV) before 1996 First discovered in 1937 in the West Nile district of Uganda Mild feverish illness Severe illness, like meningitis or encephalitis, was rare Wide distribution in Asia, Eastern Europe, Africa WNV is an Arthropod-Borne virus:  WNV is an Arthropod-Borne virus Transmitted by mosquitoes Can infect people and other animals Similar to some other viruses (a Flavivirus, in the Japanese Encephalitis Antigenic Complex – e.g. similar family to Yellow Fever, St. Louis encephalitis virus) Slide4:  West Nile virus: Approximate geographic range as of 1998 Slide5:  WNV: Basic Transmission Cycle Most important cycle is from mosquito to bird to mosquito Amplifying hosts “Incidental” infections: unlikely amplifying hosts Slide6:  1999 2000 2001 2002 Slide7:  2003 2003:  2003 WNND County Level Incidence per Million, United States, 2003*:  WNND County Level Incidence per Million, United States, 2003* Incidence per million .01-9.99 10-99.99 >=100 WNND: West Nile Neuroinvasive Disease *Reported as of 4/9/2004 Transmission:  Transmission The MOST IMPORTANT route of infection is bite of infectious mosquito 2002 revealed novel modes of transmission 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 being screened for WNV (nucleic acid amplification testing rather than antibody screening) Testing being conducted under IND Minipool vs. individual testing Presumptive viremic donors important for surveillance Will be updated in MMWRs/website Risk through transfusion very, very low Slide12:  Mosquito Vectors Important vectors vary by geography, e.g. Culex tarsalis (western states) Culex pipiens (Midwest, and elsewhere) Culex quinquefasciatus (south) Different behaviors – some fly very long distances Feeding habits, infection rates, breeding areas all important Nearly 50 species of mosquitoes capable (at least in the lab) of transmitting WNV Culex tarsalis feeding West Nile Virus—Clinical Disease:  West Nile Virus—Clinical Disease Slide14:  ~80% Asymptomatic ~20% “West Nile Fever” <1% CNS disease ~10% fatal (<0.1% of total infections) WNV Human Infection “Iceberg” For every case of illness involving the brain or spinal cord, ~150 total infections Very crude estimates WNV Fever:  WNV Fever Most people who get sick from WNV infection have WNV fever Time from exposure (usually by mosquito bite): 3-14 days Fever, chills, headache, fatigue Can be severe Nausea, vomiting (can be severe) 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 Similar to other meningitis from viruses Fever, headache, meningismus (neck stiffness, light bothering eyes) 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 People who are older (over 50) and/or who have chronic medical problems are usually the ones to have WNV encephalitis WNV Encephalitis :  WNV Encephalitis There are a number of other problems that people with WNV encephalitis may suffer: Tremor Myoclonus Quick, uncontrolled muscle jerking Problems with balance Dizziness WNV-Associated Flaccid Paralysis:  WNV-Associated Flaccid Paralysis Seen more frequently over the last 2 years Unclear how often it is happening: May be present in almost 15% of people with severe illness Affects relatively young people who are often healthy otherwise May not have fever or headache before paralysis WNV-Associated “Poliomyelitis-like illness”:  WNV-Associated “Poliomyelitis-like illness” Most cases of WNV-associated weakness that is persistent Clinical hallmarks: Onset early in infection Weakness can often be in only one limb Absence of numbness; pain sometimes present Diagnosis of WNV Infection (1):  Diagnosis of WNV Infection (1) Based on high index of clinical suspicion and obtaining specific laboratory tests Consider WNV, or other arboviral diseases such as St. Louis encephalitis, (esp. in adults >50 years) w/ unexplained encephalitis or meningitis (esp. in summer or early fall). The local presence of WNV enzootic (bird, mosquito, vet) activity or other human cases should further raise suspicion. Recent travel history also important. Diagnosis (2):  Diagnosis (2) Testing obtained through local or state health departments and increasingly through private labs Public health laboratories usually perform an IgM antibody capture enzyme-linked immunosorbent assay (MAC-ELISA). W/ this test virus-specific IgM can be detected in nearly all CSF and serum specimens from WNV-infected patients at time of clinical presentation Serum IgM antibody may persist for + 1 yr., so physicians must determine whether the antibody is result of a previous WNV infection and unrelated to the current clinical presentation. Diagnosis (3):  Diagnosis (3) Most conclusive to identify person w/CNS infection is WNV-specific IgM in CSF using MAC-ELISA. Strongly suggests acute CNS infection. If no CSF and using serum samples, paired acute and convalescent-phase samples should be acquired. Acute at initial presentation, convalescent 7-14 days later. If no convalescent sample, acute specimen should be tested w/ MAC-ELISA. If IgM neg, acute WNV infection unlikely. If IgM pos and clinically compatible may be recent WNV infection (see note about other flavivirus infections). Diagnosis (4):  Diagnosis (4) Ideally MAC-ELISA should be performed using WNV and SLE viruses If WNV and SLE results similar – necessary to use PRNT to confirm. Recent vaccination (e.g. yellow fever) or related flavivirus infection may (e.g. dengue) may result in positive WNV MAC-ELISA. See: http://www.cdc.gov/ncidod/dvbid/westnile/resources/fact_sheet_clinician.htm Reporting:  Reporting Reporting procedures vary by state – refer to state coordinators/state websites Neuroinvasive disease is nationally notifiable, fever is not. States differ in their reporting of these. WNV: Illness Outcomes:  WNV: Illness Outcomes Current information limited Fatality rates 10-20% with severe disease die Fatalities primarily among elderly, immunosuppressed Unknown why some people do not get sick and some get extremely sick WNV—Long-term problems: “When will I get better?”:  WNV—Long-term problems: “When will I get better?” Fatigue Headache Difficulty with concentration or memory However—most people eventually DO get better (based on limited observations to date) May take many months WNV-Long-term outcomes:  WNV-Long-term outcomes WNV Poliomyelitis-like illness Outcomes vary Some people from 2002 and 2003 have had dramatic, almost complete recovery; others have had continued weakness We do not know why some people improve and some do not BUT Those with less severe initial weakness tend to have a better prognosis WNV--Treatment:  WNV--Treatment As is true for most viruses that cause human illness, there is no specific treatment for WNV Studies of: Antisense WNV-RNA Interferon-α WNV-specific immune globulin (“IVIG”) Results are only preliminary now Basic problem—drug has to be given very early, almost before the person is very sick Q: Once someone gets infected with WNV, can they get sick with WNV again?:  Q: Once someone gets infected with WNV, can they get sick with WNV again? A: If someone was sick with WNV last summer, they are probably immune. We think that this immunity lasts a long time (many years). However, mosquitoes can carry other viruses that can make people sick, so they should still take care to avoid mosquito bites! Q: When a person tests positive for WNV, does that mean that the virus is still in them?:  Q: When a person tests positive for WNV, does that mean that the virus is still in them? A: By the time someone gets sick, the virus is long-gone. The test measures the body’s reaction to the virus, to determine if the virus was present in the body recently or in the more distant past. Q: What is the status of a human vaccine for WNV?:  Q: What is the status of a human vaccine for WNV? A: Several agencies and companies are working on a vaccine for humans, and one is planned for testing next year. WNV Prevention:  WNV Prevention Treatment is symptomatic – therefore prevention of illness is crucial Preventive measures Personal Household Community / environmental WNV—Personal Protection:  WNV—Personal Protection Use mosquito repellent DEET (skin or clothing) Up to 50% concentration Permethrin (clothing) Wear long sleeves, pants Emphasize protection at times of high mosquito activity (dawn/dusk) or stay indoors Protect your house and yard Use/ fix screens Air-conditioning Empty water (breeding sites) Slide35:  After getting sick, recovery can take a long time, but most people do improve Avoiding getting bitten by mosquitoes is the only way to prevent WNV There is no treatment, but people are working very hard to develop one

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