Epidemic West Nile virus encephalitis in Tunisia

Area of Science:

• Virology
• Epidemiology
• Neurology

Background:

• West Nile fever (WNF) is a mosquito-borne flavivirus infection prevalent in Africa and Asia.
• An epidemic of WNF occurred in the Sfax area of Tunisia in autumn 1997.

Purpose of the Study:

• To investigate the clinical and etiological aspects of a West Nile virus (WNV) epidemic affecting the central nervous system (CNS).
• To confirm WNV infection in hospitalized patients presenting with aseptic meningitis and/or encephalitis.

Main Methods:

• Serological testing using ELISA to detect anti-WNV antibodies in serum and cerebrospinal fluid (CSF).
• Molecular detection of the WNV genome in CSF and brain tissue using reverse transcriptase-polymerase chain reaction (RT-PCR).
• Clinical data collection, including patient demographics, symptoms, CSF analysis, and neuroimaging (CT-scan, MRI).

Main Results:

• WNV infection was confirmed in 30 patients, probable in 17, and excluded in 10.
• Patients with encephalitis were older than those with meningitis.
• CSF analysis revealed pleocytosis, elevated protein levels (47%), and normal glucose. Neuroimaging was normal.
• WNV genome was detected by RT-PCR in CSF (2 cases) and brain tissue (1 case).
• Three patients died, while others had a favorable prognosis. Autopsies showed nonspecific encephalitis lesions.

Conclusions:

• This study confirms the first WNV encephalitis epidemic in the Sfax area, Tunisia.
• CNS involvement in WNF, particularly encephalitis in older individuals, appears to carry a poor prognosis.
• Early diagnosis and understanding the epidemiology of WNV are crucial for public health management.