West Nile Virus Infection Rim Kahloun, MD Salim Ben Yahia, MD Moncef Khairallah, MD Department of ophthalmology Fattouma Bourguiba University Hospital Faculty of Medicine, University of Monastir Monastir, Tunisia

History A 52-year-old woman History: diabetes

Presentation Visual acuity: 20/25 OD, 20/32 OS No cells in anterior chamber or vitreous OU Intraocular pressure: 14 mm Hg OU Mild cataract OU Fundus OU: Inactive multifocal chorioretinitis

Fundus photography shows inactive multifocal chorioretinitis OU Fundus photography shows inactive multifocal chorioretinitis OU. Note the presence of mild non proliferative diabetic retinopathy.

Fluorescein angiography Mid-phase fluorescein angiogram shows central hypofluorescence and peripheral hyperfluorescence of chorioretinal lesions (“target-like” appearance). Note the linear clustering of chorioretinal lesions, especially OS.

Initial work-up For causes of multifocal chorioretinitis: - Syphilis - Tuberculosis - Sarcoidosis - Histoplasmosis - Idiopathic multifocal chorioretinitis Negative

Work-up History retaking: Episode of febrile illness with severe headache six months before presentation (during the summer season) Serology: positive for West Nile virus (WNV)

Treatment No specific treatment Supportive Symptomatic for ophthalmic complications

Conclusion WNV infection is a worldwide zoonotic disease caused by a single-stranded RNA flavivirus, transmitted to human by a mosquito vector (type Culex ) with wild birds serving as its reservoir Most human WNV infections are subclinical (80%) or manifest as febrile illness (20%) and occur in last summer and autumn. Severe neurologic disease (meningoencephalitis) occurs in less than 1% of patients and is associated with advanced age and diabetes

Conclusion Typical bilateral or rarely unilateral multifocal chorioretinitis is the most common ocular manifestation of WNV infection The unique pattern of multifocal chorioretinitis can help establish an early diagnosis of the disease while serologic testing is pending