Lyle R. Petersen, MD, MPH; Anthony A. Marfin, MD, MPH
Current Author Addresses: Drs. Petersen and Marfin: Division of Vector-borne Infectious Diseases, Centers for Disease Control and Prevention, PO Box 2087 (Foothills Campus), Fort Collins, CO 80522.
This paper provides the clinician with an understanding of the epidemiologic and biological characteristics of West Nile virus in North America, as well as useful information on the diagnosis, reporting, and management of patients with suspected West Nile virus infection and on advising patients about prevention. Information was gathered from the medical literature and from national surveillance data through May 2002. Since the identification of West Nile virus in New York City in 1999, enzootic activity has been documented in 27 states and the District of Columbia. Continued geographic expansion is likely. Overall, one in 150 infections results in severe neurologic illness. Advanced age is by far the most important risk factor for neurologic disease and, once disease develops, for worse clinical outcome. Surveillance has identified 149 persons with West Nile virus–related illness in 10 states. Encephalitis is more commonly reported than meningitis, and concomitant muscle weakness and flaccid paralysis may provide a clinical clue to the presence of West Nile virus infection. Peak incidence occurs in late summer, although onset has occurred from July through December. Immunoglobulin M antibody testing of serum specimens and cerebrospinal fluid is the most efficient method of diagnosis, although cross-reactions are possible in patients recently vaccinated against or recently infected with related flaviviruses. Testing can be arranged through local, state, or provincial (in Canada) health departments. Prevention rests on elimination of mosquito breeding sites; judicious use of pesticides; and avoidance of mosquito bites, including mosquito repellent use.
Table 1. Key Clinical Facts about West Nile Virus in North America
States reporting epizootic activity and human infections of the West Nile virus, 1999–2001.
Week of symptom onset for persons reported to have West Nile virus infection, 1999–2001.
Transmission cycle of West Nile virus.
Table 2. Symptoms of West Nile Virus Reported among Hospitalized Patients during Outbreaks in New York State (1999), Romania (1996), and Israel (2000)
Table 3. U.S. National Case Definitions for West Nile Encephalitis
The In the Clinic® slide sets are owned and copyrighted by the American College of Physicians (ACP). All text, graphics, trademarks, and other intellectual property incorporated into the slide sets remain the sole and exclusive property of the ACP. The slide sets may be used only by the person who downloads or purchases them and only for the purpose of presenting them during not-for-profit educational activities. Users may incorporate the entire slide set or selected individual slides into their own teaching presentations but may not alter the content of the slides in any way or remove the ACP copyright notice. Users may make print copies for use as hand-outs for the audience the user is personally addressing but may not otherwise reproduce or distribute the slides by any means or media, including but not limited to sending them as e-mail attachments, posting them on Internet or Intranet sites, publishing them in meeting proceedings, or making them available for sale or distribution in any unauthorized form, without the express written permission of the ACP. Unauthorized use of the In the Clinic slide sets will constitute copyright infringement.
Lyle R. Petersen, Anthony A. Marfin. West Nile Virus: A Primer for the Clinician. Ann Intern Med. 2002;137:173–179. doi: 10.7326/0003-4819-137-3-200208060-00009
Download citation file:
Published: Ann Intern Med. 2002;137(3):173-179.
CNS Infections, Infectious Disease, Neurology.
Results provided by:
Copyright © 2017 American College of Physicians. All Rights Reserved.
Print ISSN: 0003-4819 | Online ISSN: 1539-3704
Conditions of Use