West Nile Encephalitis Clinical Presentation

  • Author: Burke A Cunha, MD; Chief Editor: Michael Stuart Bronze, MD   more...
 
Updated: Jun 17, 2011
 

History

Mosquito bites

Patients may not provide a mosquito bite history. The incubation period of West Nile encephalitis (WNE) is 1-6 days and is perhaps as long as 14 days in immunosuppressed patients.

Symptoms

A study by the American Red Cross concluded that 26% of all patients with West Nile virus infection become symptomatic.[7] They noted that although 50% of infected individuals did seek some type of medical attention, only 5% were diagnosed as having WNE. The risk of developing symptoms was correlated with higher viral loads and female sex.

Most people who are infected (at least most children) are asymptomatic or have a flulike illness. A minority of people develop neurologic disease.

Many patients describe prominent GI symptoms, especially vomiting and diarrhea. Nonspecific symptoms may include sore throat, backache, myalgias, and arthralgias. Most patients with WNE present with features of encephalitis, aseptic meningitis (meningoencephalitis), or both.

Symptoms include a mild febrile illness accompanied by headache, mental confusion, tremors, or flaccid paralysis. Symptoms are most prominent in very young and very old people.

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Physical Examination

The extent and severity of central nervous system (CNS) viral invasion determine the clinical expression of WNE. Most patients are febrile or have low-grade fevers.

Patients who present with encephalitis have mental confusion or disorientation and may have decreased consciousness. Patients with severe cases of West Nile encephalitis (WNE) may present with stupor or coma.

Multifocal chorioretinitis is the most common ophthalmologic manifestation of WNE.[8] Ten percent of patients with WNE have an enlarged liver. Approximately 20% have splenomegaly. CNS findings include a stiff neck with meningeal signs, including positive Kernig or Brudzinski signs in patients with aseptic meningitis or meningoencephalitis. Some cases of WNE are accompanied by mild, nonexudative pharyngitis. Generalized adenopathy and an enlarged submental node are uncommon (1%).[9]

A study found that approximately 20% of patients in the New York City area who were infected with West Nile virus during a 1999 outbreak presented with truncal maculopapular rash.[9]

Consider WNE in patients who have encephalitis and otherwise unexplained extremity weakness and/or paralysis.

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Contributor Information and Disclosures
Author

Burke A Cunha, MD  Professor of Medicine, State University of New York School of Medicine at Stony Brook; Chief, Infectious Disease Division, Winthrop-University Hospital

Burke A Cunha, MD is a member of the following medical societies: American College of Chest Physicians, American College of Physicians, and Infectious Diseases Society of America

Disclosure: Nothing to disclose.

Specialty Editor Board

Wesley W Emmons, MD, FACP  Assistant Professor, Department of Medicine, Thomas Jefferson University; Consulting Staff, Infectious Diseases Section, Department of Internal Medicine, Christiana Care, Newark, DE

Wesley W Emmons, MD, FACP is a member of the following medical societies: American College of Physicians, American Medical Association, American Society of Tropical Medicine and Hygiene, Infectious Diseases Society of America, and International AIDS Society

Disclosure: Nothing to disclose.

Francisco Talavera, PharmD, PhD  Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Medscape Salary Employment

John L Brusch, MD, FACP  Assistant Professor of Medicine, Harvard Medical School; Consulting Staff, Department of Medicine and Infectious Disease Service, Cambridge Health Alliance

John L Brusch, MD, FACP is a member of the following medical societies: American College of Physicians and Infectious Diseases Society of America

Disclosure: Nothing to disclose.

Chief Editor

Michael Stuart Bronze, MD  Professor, Stewart G Wolf Chair in Internal Medicine, Department of Medicine, University of Oklahoma Health Science Center

Michael Stuart Bronze, MD is a member of the following medical societies: Alpha Omega Alpha, American College of Physician Executives, American College of Physicians, American College of Physicians-American Society of Internal Medicine, American Federation for Clinical Research, American Medical Association, American Society for Microbiology, Association of Professors of Medicine, Association of Program Directors in Internal Medicine, Infectious Diseases Society of America, Oklahoma State Medical Association, and Southern Society for Clinical Investigation

Disclosure: Nothing to disclose.

References

  1. Cunha BA. Alexander the Great and West Nile virus encephalitis. Emerg Infect Dis. Jul 2004;10(7):1328-9; author reply 1332-3. [Medline].

  2. Oldach D, Benitez RM, Mackowiak PA. Alexander the Great and West Nile virus encephalitis. Emerg Infect Dis. Jul 2004;10(7):1329-30; author reply 1332-3. [Medline].

  3. MacDonald RD, Krym VF. West Nile virus. Primer for family physicians. Can Fam Physician. Jun 2005;51:833-7. [Medline]. [Full Text].

  4. Petersen LR, Marfin AA. West Nile virus: a primer for the clinician. Ann Intern Med. Aug 6 2002;137(3):173-9. [Medline].

  5. Murray K, Baraniuk S, Resnick M, Arafat R, Kilborn C, Cain K, et al. Risk factors for encephalitis and death from West Nile virus infection. Epidemiol Infect. Dec 2006;134(6):1325-32. [Medline]. [Full Text].

  6. Wadei H, Alangaden GJ, Sillix DH, et al. West Nile virus encephalitis: an emerging disease in renal transplant recipients. Clin Transplant. Dec 2004;18(6):753-8. [Medline].

  7. Zou S, Foster GA, Dodd RY, Petersen LR, Stramer SL. West Nile fever characteristics among viremic persons identified through blood donor screening. J Infect Dis. Nov 1 2010;202(9):1354-61. [Medline].

  8. Abroug F, Ouanes-Besbes L, Letaief M, et al. A cluster study of predictors of severe West Nile virus infection. Mayo Clin Proc. Jan 2006;81(1):12-6. [Medline]. [Full Text].

  9. Nash D, Mostashari F, Fine A, et al. The outbreak of West Nile virus infection in the New York City area in 1999. N Engl J Med. Jun 14 2001;344(24):1807-14. [Medline].

  10. Rodriguez AJ, Westmoreland BF. Electroencephalographic characteristics of patients infected with west nile virus. J Clin Neurophysiol. Oct 2007;24(5):386-9. [Medline].

  11. Rawal A, Gavin PJ, Sturgis CD. Cerebrospinal fluid cytology in seasonal epidemic West Nile virus meningo-encephalitis. Diagn Cytopathol. Feb 2006;34(2):127-9. [Medline].

  12. Tyler KL, Pape J, Goody RJ, et al. CSF findings in 250 patients with serologically confirmed West Nile virus meningitis and encephalitis. Neurology. Feb 14 2006;66(3):361-5. [Medline].

  13. Murray KO, Resnick M, Miller V. Depression after infection with West Nile virus. Emerg Infect Dis. Mar 2007;13(3):479-81. [Medline]. [Full Text].

  14. Ou AC, Ratard RC. One-year sequelae in patients with West Nile Virus encephalitis and meningitis in Louisiana. J La State Med Soc. Jan-Feb 2005;157(1):42-6. [Medline].

  15. Sejvar JJ. The long-term outcomes of human West Nile virus infection. Clin Infect Dis. Jun 15 2007;44(12):1617-24. [Medline].

  16. Cunha BA. Differential diagnosis of West Nile encephalitis. Curr Opin Infect Dis. Oct 2004;17(5):413-20. [Medline].

  17. Cunha BA, Minnaganti V, Johnson DH, Klein NC. Profound and prolonged lymphocytopenia with West Nile encephalitis. Clin Infect Dis. Oct 2000;31(4):1116-7. [Medline].

  18. Cunha BA, Sachdev B, Canario D. Serum ferritin levels in West Nile encephalitis. Clin Microbiol Infect. Feb 2004;10(2):184-6. [Medline].

 
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Common encephalitis associations.
Clinical features of arboviral encephalitis.
Differential diagnoses of meningoencephalitis.
The Culex mosquito, common in the eastern United States, is the primary vector responsible for infecting humans with West Nile virus. Prevention of West Nile virus is primarily directed at reducing the mosquito population from May to October and by taking precautions to limit human exposure during these months of high mosquito activity. Image courtesy of the Centers for Disease Control and Prevention.
The geographic distribution of the Japanese encephalitis servocomplex of the family Flaviridae, 2000. Image courtesy of the Centers for Disease Control and Prevention.
States reporting laboratory-positive West Nile virus infection in birds, mosquitoes, animals, or humans between January 1 and August 28, 2002. Image courtesy of the Centers for Disease Control and Prevention.
 
 
 
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