Most West Nile virus infections are mild and often clinically unapparent.
Reports from earlier outbreaks describe the mild form of West Nile virus infection as a febrile illness of sudden onset often accompanied by
Approximately 1 in 150 infections will result in severe neurological disease.
In recent outbreaks, symptoms occurring among patients hospitalized with severe disease include:
Diagnosis of West Nile virus infection is based on a high index of clinical suspicion and obtaining specific laboratory tests.
Note: Severe neurological disease due to West Nile virus infection has occurred in patients of all ages. Year-round transmission is possible in some areas. Therefore, West Nile virus should be considered in all persons with unexplained encephalitis and meningitis.
Procedures for submitting diagnostic samples and reporting persons with suspected West Nile virus infection vary among states and jurisdictions. Links to state and local websites are available at www.cdc.gov/ncidod/dvbid/westnile/city_states.htm.
Procedures for submitting specimens to the Illinois Department of Public Health Laboratory and requisition forms can be found at www.idph.state.il.us/envhealth/wnvguidelines.htm. Go to Health Care Provider information and then click on West Nile Virus Testing Guidelines.
West Nile virus testing for patients with encephalitis or meningitis can be obtained through local or state health departments.
Refer to local and state health department reporting requirements: www.cdc.gov/ncidod/dvbid/westnile/city_states.htm
In Illinois, cases of arboviral disease, such as West Nile virus, are required to be reported to the local health department. Contact information for local health departments can be found at www.idph.state.il.us/local/home.htm.
The timely identification of persons with acute West Nile virus 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.
Among patients in recent outbreaks
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 West Nile virus 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 West Nile virus 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.
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 www.cdc.gov/ncidod/dvbid/westnile/surv&control.htm
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