Department of Land Resources & Environmental Sciences
 Montana State University
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©2004 RKD Peterson

West Nile Virus

Symptoms



Introduction

Most WNV infections are symptomless (Tsai et al. 1998, Mostashari et al. 2001, Petersen et al. 2003). The incubation period is usually 2 to 14 days (Campbell et al. 2002, Petersen and Marfin 2002) but 21 days of incubation period were observed in transplant recipients (Iwamoto et al. 2003). About 1 person in 5 (20%) develops flu-like symptoms (Mostashari et al. 2001, Fratkin et al. 2004, Guharoy et al. 2004). Only 1 person in 150 (0.67%) develops acute neurological disease (meningitis or encephalitis) (Mostashari et al. 2001, Sejvar et al. 2003a, Fratkin et al. 2004).
          A variety of symptoms can be associated with WNV infection. The most common ones are: fever, weakness, headache, altered mental status, gastrointestinal symptoms such as nausea and vomiting, and myalgia (Asnis et al. 2001, Nash et al. 2001, Weinberger et al. 2001, Weiss et al. 2001, Berner et al. 2003, Emig and Apple 2003, Pepperell et al 2003, Sejvar et al 2003a, Brilla et al. 2004, Guharoy et al. 2004). Other symptoms include anorexia, seizures and vertigo, photophobia, rash, generalized hypo- or areflexia, abnormal hyperreflexia, lymphadenopathy, blurred vision, diplopia, ophthalmoplegia, and others (Asnis et al. 2001, Nash et al. 2001, Weinberger et al. 2001, Weiss et al. 2001, Berner et al. 2003, Emig and Apple 2003, Pepperell et al 2003, Sejvar et al 2003a, Brilla et al. 2004, Guharoy et al. 2004).   
          WN fever patients are usually those who had positive results for WNV but did not meet the definitions for meningitis, encephalitis or acute flaccid paralysis. A patient is diagnosed as having WN encephalitis if he or she presents fever, headache, encephalopathy, or altered mental status ranging from confusion to coma with or without additional signs of brain dysfunction (CDC 2001, Weiss et al. 2001, Sejvar et al. 2003a, Brilla et al. 2004). WN meningitis is characterized by fever, headache, and clinical signs of meningeal inflammation such as stiff neck and/or photophobia, and pleocytosis (CDC 2001, Weiss et al. 2001, Sejvar et al. 2003a, Brilla et al. 2004). Weiss et al. (2001) classified patients as having meningoencephalitis if they met both criteria. Another possible classification of patients with WNV infection is acute flaccid paralysis, which is characterized by acute onset of limb weakness, areflexia/hyporeflexia, numbness of affected limbs, involvement of spinal cord gray matter (Weiss et al. 2001, Sejvar et al. 2003a,b). Patients can present acute flaccid paralysis with other neurological involvement (encephalitis or meningitis) or not.

Epidemiology
Symptoms
Risk Factors
Morbidity
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References

Asnis, D.S., R. Conetta, G. Waldman, and A. A. Teixeira. 2001. The West Nile Virus Encephalitis Outbreak in the United States (1999-2000) – From Flushing, New York, to beyond its borders. Ann. N. Y. Acad. Sci. Dec 2001, 951: 161-171.

Berner, Y.N., R. Lang, and M.Y. Chowers. 2003. Outcome of West Nile Fever in Older Adults. J. Am. Geriatr. Soc. 51: 1844-1846.

Brilla, R., M. Block, G. Geremia, and M. Witcher. 2004. Clinical and neuroradiological features of 39 consecutive cases of West Nile meningoencephalitis. J. Neurol. Sci. 220: 37-40.

CDC - Centers for Disease Control and Prevention. 2001. Encephalitis or meningitis, arboviral. 2001 case definition. Accessed at www.cdc.gov/epo/dphsi/casedef/encephalitiscurrent.htm on 28 March 2005.

Emig, M. and D.J. Apple. 2003. Sever West Nile Disease in Healthy Adults. Clin. Infec. Dis.38(2): 289-292.

Fratkin, J.D., A.A. Leis, D.S. Stokic, S.A. Slavinski, and R.W. Geiss. 2004. Spinal cord neuropathology in human West Nile virus infection. Arch. Pathol. Lab. Med. 128: 533-537.

Guharoy, R., S.A. Gilroy, J.A. Noviasky, and J. Ference. 2004. West Nile virus infection. Am. J. Heath-Syst. Pharm. 61: 1235-1241.

Iwamoto, M., D.B. Jernigan, A. Guasch, M.J. Trepka, C.G. Blackmore, W.C. Hellinger, S.M. Pham, S. Zaki, R.S. Lanciotti, S.E. Lance-Parker, C.A. DiazGranados, A.G. Winquist, C.A. Perlino, S. Wiersma, K.L. Hillyer, J.L. Goodman, A.A. Marfin, M.E. Chamberland, and L.R. Petersen. 2003. Transmission of West Nile virus from an organ donor to four transplant recipients. N. Engl. J. Med. 348(22): 2196-2203.

Mostashari, F., M.L. Bunning, D.A. Singer, D. Nash, M.J. Cooper, N. Katz, K.A. Liljebjelke, B.J. Biggerstaff, A. D. Fine, M.C. Layton, S.M.Mullin, A.J. Johnson, D.A. Martin, E.B. Hayes, and G. L. Campbell. 2001. Epidemic West Nile encephalitis, New York, 1999: results of a household-based seroepidemiological survey. Lancet Infect. Dis. 358: 261-264.

Nash, D., F. Mostashari, A. Fine, J. Miller, D. O’Leary, K. Murray, A. Huang, A. Rosenberg, A. Greenberg, M. Sherman, S. Wong, and M. Layton. 2001. The outbreak of West Nile virus infection in the New York City area in 1999. N. Engl. J. Med. 344(24): 1807-1814.

Pepperell, C., N. Rau, S. Krajden, R. Kern, A. Humar, B. Mederski, A. Simor, D.E. Low, A. McGeer, T. Mazzulli, J. Burton, C. Jaigobin, M. Fearon, H. Artsob, M.A. Drebot, W. Halliday, and J. Brunton. 2003. West Nile virus infection in 2002: morbidity and mortality among patient admitted to hospital in southcentral Ontario. CMAJ. 168(11): 1399-1405.

Petersen, L.R., A.A. Marfin, and D.J. Gubler. 2003. West Nile Virus. JAMA 290(4): 524-528.

Sejvar, J.J., M.B. Haddad, B.C. Tierney, G.L. Campbell, A.A. Marfin, J.A. Van Gerpen, A. Fleischauer, A.A. Leis, D.S. Stokic, and L.R. Petersen. 2003a. Neurologic manifestations and outcome of West Nile virus infection. JAMA 290(4): 511-515.

Sejvar, J.J., A.A. Leis, D.S. Stokic, J.A. Van Gerpen, A.A. Marfin, R. Webb, M.B. Haddad, B.C. Tierney, S.A. Slavinski, J.L. Polk, V. Dostrow, M. Winkelmann, and L.R. Petersen. 2003b. Acute Flaccid Paralysis and West Nile Infection. Emerg. Infect. Dis. 9(7): 788-793.

Tsai, T.F., F. Popovici, G.L. Campbell, and N.I. Nedelcu. 1998. West Nile encephalitis epidemic in southeastern Romania. Lancet Infec. Dis. 352: 1-5.

Weinberger, M., S.D. Pitlik, D. Gandacu, R. Lang, F. Nassar, D.B. David, E. Rubinstein, A. Izthaki, J. Mishal, R. Kitzes, Y. Siegman-Igra, M. Giladi, N.Pick, E. Mendelson, H. Bin, T. Shohat, and M.Y. Chowers. 2001S. West Nile Fever outbreak, Israel, 2000: Epidemiologic Aspects. Emerg. Infec. Dis. 7(4): 686-691.

Weiss, D., D. Carr, J. Kellachan, C. Tan, M. Philips, E. Bresnitz, and M. Layton. 2001. Clinical findings of West Nile virus infection in hospitalized patients, New York and New Jersey, 2000. Emerg. Infec. Dis. 7(4): 654-658.
 
 
 
 
 
 

 

Although we provide general information on West Nile Virus (WNV), this web site is designed primarily to provide information on human-health and ecological risk assessments of WNV and tactics used for mosquito management.