ORIGINAL ARTICLE
A Cluster Study of Predictors of Severe West Nile Virus Infection

https://doi.org/10.4065/81.1.12Get rights and content

OBJECTIVE

To assess the value of multifocal chorioretinitis and of clinical manifestations and biologic parameters in the diagnosis of West Nile virus (WNV) infection.

PATIENTS AND METHODS

We conducted a prospective, controlled case series study during an outbreak of WNV infection between August 15 and October 24, 2003, of 64 consecutive patients who presented with clinical manifestations consistent with WNV disease. In each patient, standardized clinical and biologic data were collected. An ophthalmologic examination searching particularly for multifocal chorioretinitis was performed.

RESULTS

Of 64 patients who presented primarily with meningitis and/or encephalitis, 36 had IgM antibodies against WNV. The WNV-infected patients tended to be older (median age of 54 years vs 46 years in WNV infection and control groups, respectively) and more frequently had diabetes (30% vs 7% in WNV infection and control groups, respectively; P=.03). Multifocal chorioretinitis was found in 75% of WNV-infected patients but in no patient in the control group (P=.001). Blood glucose and amylase levels were higher in WNV-infected patients, whereas serum sodium levels were lower. The cerebrospinal fluid leukocyte count and protein levels were significantly higher in WNV meningitis or encephalitis. Overall, multifocal chorioretinitis had 100% specificity and 73% sensitivity (88% when only patients with meningitis or encephalitis were analyzed) for the diagnosis of WNV. Multivariate analysis disclosed multifocal chorioretinitis as the only predictor of WNV infection (odds ratio, 62; 95% confidence interval, 6-700; P=.001).

CONCLUSION

Multifocal chorioretinitis appears to be a specific marker of WNV infection, particularly in patients who present with meningoencephalitis. An ophthalmologic examination should be part of the routine evaluation of such patients.

Section snippets

PATIENTS AND METHODS

During an outbreak of WNV infection that occurred in the region of Monastir, Tunisia, between August 15 and October 24, 2003, 64 patients aged 20 to 85 years were consecutively hospitalized in the infectious diseases ward (n=44) or in the intensive care unit (n=20) for clinical manifestations consistent with WNV infection. All patients were immunocompetent and presented with evidence of an acute infection (fever, elevated white blood cell count, and elevated C-reactive protein level), along

RESULTS

A diagnosis of infection with WNV was confirmed in 36 (56%) of the 64 patients. IgM antibodies to WNV were detected in the CSF (n=31) or in serum (n=5). None of the remaining 28 patients had positive WNV test results in blood or CSF, and polymerase chain reaction of the CSF produced positive results in 12 patients for enteroviruses and in 4 patients for herpes simplex virus. The clinical characteristics of patients with WNV infection and of the control group are given in Table 1. The

DISCUSSION

Our study shows that a unique multifocal chorioretinitis is a frequent and specific marker of WNV infection. Infection with WNV is an emerging infectious disease that remains a diagnostic challenge for clinicians in the absence of specific clinical features that allow distinguishing WNV from other causes of viral encephalitis. Therefore, additional clinical tools for diagnosis are needed. Sejvar et al1 recently emphasized the frequent occurrence of movement disorders and parkinsonism in WNV

CONCLUSION

Multifocal chorioretinitis with a typical funduscopic appearence unique to WNV infection is highly suggestive of the disease. Ophthalmologic examination should be part of the routine examination of a patient in whom WNV infection is considered, particularly when a clinical syndrome of viral meningoencephalitis is present.

Acknowledgments

We are indebted to Professor Christian Brun Buisson (Hôpital Henri Mondor, Créteil, France) for his help in preparation of the submitted manuscript.

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