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Esta pagina en Espanol | | | | | +---------------+--------------------+---------------+-----------------------------------------------------------+--------------+----------------+------------------+-----------------+ | Public Inquiries | | | | | | English: | | | | | | (888) 246-2675 | | | | | | Espanol: | | | | | | (888) 246-2857 | | | | | | TTY: | | | | | | (866) 874-2646 | | | | | | | | | | | | Mon-Fri 8am-11pm EST | | | | | | Sat-Sun 10am-8pm EST | | | | | +---------------+--------------------+---------------+-----------------------------------------------------------+--------------+----------------+------------------+-----------------+ | | | West Nile Virus Home > Clinical Guidance > West Nile | | | | | | | | Virus (WNV) Infection: Information for Clinicians | | | | | | | | | | | | | | | | Fact Sheet: | | | | | | | | West Nile Virus (WNV) Infection: Information for | | | | | | | | Clinicians | | | | | | | | | | | | | | | | Clinical Features | | | | | | | | | | | | | | | | Mild Infection | | | | | | | | | | | | | | | | Most WNV infections are mild and often clinically | | | | | | | | unapparent. | | | | | | | | | | | | | | | | --------------------------------------------------------- | | | | | | | | * Approximately 20% of those infected develop a mild | | | | | | | | illness (West Nile fever). | | | | | | | | --------------------------------------------------------- | | | | | | | | * The incubation period is thought to range from 3 to 14 | | | | | | | | days. | | | | | | | | --------------------------------------------------------- | | | | | | | | * Symptoms generally last 3 to 6 days. | | | | | | | | | | | | | | | | Reports from earlier outbreaks describe the mild form of | | | | | | | | WNV infection as a febrile illness of sudden onset often | | | | | | | | accompanied by | | | | | +---------------+--------------------+---------------+-----------------------------------------------------------+--------------+----------------+------------------+-----------------+ | | | | malaise | | headache | | +---------------+--------------------+---------------+-----------------------------------------------------------+--------------+----------------+------------------+-----------------+ | | | | anorexia | | myalgia | | +---------------+--------------------+---------------+-----------------------------------------------------------+--------------+----------------+------------------+-----------------+ | | | | nausea | | rash | | +---------------+--------------------+---------------+-----------------------------------------------------------+--------------+----------------+------------------+-----------------+ | | | | vomiting | | lymphadenopathy | | +---------------+--------------------+---------------+-----------------------------------------------------------+--------------+----------------+------------------+-----------------+ | | | | eye pain | | | | +---------------+--------------------+---------------+-----------------------------------------------------------+--------------+----------------+------------------+-----------------+ | | | The full clinical spectrum of West Nile fever has not | | | | | | | | been determined in the United States. | | | | | | | | | | | | | | | | Severe Infection | | | | | | | | | | | | | | | | Approximately 1 in 150 infections will result in severe | | | | | | | | neurological disease. | | | | | | | | | | | | | | | | --------------------------------------------------------- | | | | | | | | * The most significant risk factor for developing severe | | | | | | | | neurological disease is advanced age. | | | | | | | | --------------------------------------------------------- | | | | | | | | * Encephalitis is more commonly reported than | | | | | | | | meningitis. | | | | | | | | | | | | | | | | In recent outbreaks, symptoms occurring among patients | | | | | | | | hospitalized with severe disease include | | | | | +---------------+--------------------+---------------+-----------------------------------------------------------+--------------+----------------+------------------+-----------------+ | | | | fever | | gastrointestinal | | | | | | | | symptoms | | +---------------+--------------------+---------------+-----------------------------------------------------------+--------------+----------------+------------------+-----------------+ | | | | weakness | | change in | | | | | | | | mental status | | +---------------+--------------------+---------------+-----------------------------------------------------------+--------------+----------------+------------------+-----------------+ | | | A minority of patients with severe disease developed a | | | | | | | | maculopapular or morbilliform rash involving the neck, | | | | | | | | trunk, arms, or legs. | | | | | | | | --------------------------------------------------------- | | | | | | | | * Several patients experienced severe muscle weakness | | | | | | | | and flaccid paralysis. | | | | | | | | --------------------------------------------------------- | | | | | | | | * Neurological presentations included | | | | | +---------------+--------------------+---------------+-----------------------------------------------------------+--------------+----------------+------------------+-----------------+ | | | | | ataxia and | | optic neuritis | | | | | | extrapyramidal | | | | | | | | signs | | | +---------------+--------------------+---------------+-----------------------------------------------------------+--------------+----------------+------------------+-----------------+ | | | | | cranial nerve | | polyradiculitis | | | | | | abnormalities | | | +---------------+--------------------+---------------+-----------------------------------------------------------+--------------+----------------+------------------+-----------------+ | | | | | myelitis | | seizures | +---------------+--------------------+---------------+-----------------------------------------------------------+--------------+----------------+------------------+-----------------+ | | | Although not observed in recent outbreaks, myocarditis, | | | | | | | | pancreatitis, and fulminant hepatitis have been | | | | | | | | described. | | | | | | | | | | | | | | | | Clinical Suspicion | | | | | | | | | | | | | | | | Diagnosis of WNV infection is based on a high index of | | | | | | | | clinical suspicion and obtaining specific laboratory | | | | | | | | tests. | | | | | | | | | | | | | | | | --------------------------------------------------------- | | | | | | | | * WNV, or other arboviral diseases such as St. Louis | | | | | | | | encephalitis, should be strongly considered in adults | | | | | | | | >50 years who develop unexplained encephalitis or | | | | | | | | meningitis in summer or early fall. | | | | | | | | --------------------------------------------------------- | | | | | | | | * The local presence of WNV enzootic activity or other | | | | | | | | human cases should further raise suspicion. | | | | | | | | --------------------------------------------------------- | | | | | | | | * Obtaining a recent travel history is also important. | | | | | | | | | | | | | | | | Note: Severe neurological disease due to WNV infection | | | | | | | | has occurred in patients of all ages. Year-round | | | | | | | | transmission is possible in some areas. Therefore, WNV | | | | | | | | should be considered in all persons with unexplained | | | | | | | | encephalitis and meningitis. | | | | | | | | | | | | | | | | Diagnosis and Reporting | | | | | | | | | | | | | | | | Procedures for submitting diagnostic samples and | | | | | | | | reporting persons with suspected WNV infection vary | | | | | | | | among states and jurisdictions. Links to state and local | | | | | | | | websites are available at | | | | | | | | http://www.cdc.gov/ncidod/dvbid/westnile/city_states.htm | | | | | | | | | | | | | | | | Diagnostic Testing | | | | | | | | | | | | | | | | WNV testing for patients with encephalitis or meningitis | | | | | | | | can be obtained through local or state health | | | | | | | | departments. | | | | | | | | | | | | | | | | --------------------------------------------------------- | | | | | | | | * The most efficient diagnostic method is detection of | | | | | | | | IgM antibody to WNV in serum or cerebral spinal fluid | | | | | | | | (CSF) collected within 8 days of illness onset using the | | | | | | | | IgM antibody capture enzyme-linked immunosorbent assay | | | | | | | | (MAC-ELISA). | | | | | | | | --------------------------------------------------------- | | | | | | | | * Since IgM antibody does not cross the blood-brain | | | | | | | | barrier, IgM antibody in CSF strongly suggests central | | | | | | | | nervous system infection. | | | | | | | | --------------------------------------------------------- | | | | | | | | * Patients who have been recently vaccinated against or | | | | | | | | recently infected with related flaviviruses (e.g., | | | | | | | | yellow fever, Japanese encephalitis, dengue) may have | | | | | | | | positive WNV MAC-ELISA results. | | | | | | | | | | | | | | | | Reporting Suspected WNV Infection | | | | | | | | | | | | | | | | Refer to local and state health department reporting | | | | | | | | requirements: | | | | | | | | http://www.cdc.gov/ncidod/dvbid/westnile/city_states.htm | | | | | | | | | | | | | | | | --------------------------------------------------------- | | | | | | | | * WNV encephalitis is on the list of designated | | | | | | | | nationally notifiable arboviral encephalitides. | | | | | | | | --------------------------------------------------------- | | | | | | | | * Aseptic meningitis is reportable in some | | | | | | | | jurisdictions. | | | | | | | | | | | | | | | | The timely identification of persons with acute WNV or | | | | | | | | other arboviral infection may have significant public | | | | | | | | health implications and will likely augment the public | | | | | | | | health response to reduce the risk of additional human | | | | | | | | infections. | | | | | | | | | | | | | | | | Laboratory Findings | | | | | | | | | | | | | | | | Among patients in recent outbreaks | | | | | | | | | | | | | | | | --------------------------------------------------------- | | | | | | | | * Total leukocyte counts in peripheral blood were mostly | | | | | | | | normal or elevated, with lymphocytopenia and anemia also | | | | | | | | occurring. | | | | | | | | --------------------------------------------------------- | | | | | | | | * Hyponatremia was sometimes present, particularly among | | | | | | | | patients with encephalitis. | | | | | | | | --------------------------------------------------------- | | | | | | | | * Examination of the cerebrospinal fluid (CSF) showed | | | | | | | | pleocytosis, usually with a predominance of lymphocytes. | | | | | | | | --------------------------------------------------------- | | | | | | | | * Protein was universally elevated. | | | | | | | | --------------------------------------------------------- | | | | | | | | * Glucose was normal. | | | | | | | | --------------------------------------------------------- | | | | | | | | * Computed tomographic scans of the brain mostly did not | | | | | | | | show evidence of acute disease, but in about one-third | | | | | | | | of patients, magnetic resonance imaging showed | | | | | | | | enhancement of the leptomeninges, the periventricular | | | | | | | | areas, or both. | | | | | | | | | | | | | | | | Treatment | | | | | | | | | | | | | | | | Treatment is supportive, often involving | | | | | | | | hospitalization, intravenous fluids, respiratory | | | | | | | | support, and prevention of secondary infections for | | | | | | | | patients with severe disease. | | | | | | | | | | | | | | | | --------------------------------------------------------- | | | | | | | | * Ribavirin in high doses and interferon alpha-2b were | | | | | | | | found to have some activity against WNV in vitro, but no | | | | | | | | controlled studies have been completed on the use of | | | | | | | | these or other medications, including steroids, | | | | | | | | antiseizure drugs, or osmotic agents, in the management | | | | | | | | of WNV encephalitis. | | | | | | | | | | | | | | | | --------------------------------------------------------- | | | | | | | | | | | | | | | | For additional clinical information, please refer to | | | | | | | | Petersen LR and Marfin AA, "West Nile Virus: A Primer | | | | | | | | for the Clinician [Review]" Annals of Internal Medicine | | | | | | | | (August 6) 2002:137:173-9. | | | | | | | | PDF (287 KB/7 pages) | | | | | | | | | | | | | | | | For clinical and laboratory case definitions, see | | | | | | | | "Epidemic/Epizootic West Nile Virus in the United | | | | | | | | States: Revised Guidelines for Surveillance, Prevention, | | | | | | | | and Control, 2001," at | | | | | | | | http://www.cdc.gov/ncidod/dvbid/westnile/surv&control.htm | | | | | | | | | | | | | | | | Return to top of page | | | | | +---------------+--------------------+---------------+-----------------------------------------------------------+--------------+----------------+------------------+-----------------+ | | | | Some | | | | | | | | documents | | | | | | | | are | | | | | | | | available | | | | | | | | here in | | | | | | | | Adobe | | | | | | | | Acrobat | | | | | | | | Reader | | | | | | | | format | | | | | | | | (PDF). 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