Systemic and Ophthalmic Manifestations of West Nile Virus Infection

Yos Priestley; Marcia Thiel; Steven B. Koevary


Expert Rev Ophthalmol. 2008;3(3):279-292. 

In This Article


The most commonly reported ocular features of WNV infection are multifocal, bilateral chorioretinal lesions characteristically found in either a scattered or linear pattern.[29,66,67] A prospective study conducted in Tunisia found that 20 out of 29 patients seen with WNV had chorioretinal lesions.[62] The size of the lesions can range from 100 to 1500 µm, with most being 200-500 µm. Active lesions have distinct margins, appear circular, flat, deep and whitish/yellow in color upon ophthalmoscopy, are typically found in the midzone and periphery of the temporal and superior nasal quadrants and may also involve the posterior pole.[62,63] Inactive lesions are partially atrophic and partially pigmented with a central hypoflorescence and a peripheral hyperflorescence upon fluorescence angiography, resulting in a target-like appearance. A study by Khairallah et al. suggests that chorioretinal lesions are best observed using indocyanine green (ICG) (Figure 1) rather than ophthalmoscopy (Figure 2) and fluorescence angiography (FA) (Figure 3).[65] While it was suggested that the virus causes chorioretinitis by seeding the choroid by hematogenous dissemination during viremia,[29] other data indicate that that the characteristic linear pattern seen in 80% of cases[62] develops in parallel with the path of retinal nerve fibers, suggesting that the virus spreads from the CNS to the retina, RPE and choroid by way of the optic nerve.[67] Vitritis is often seen in patients with chorioretinitis; there has been only one reported case of stand-alone vitritis.[29]

Figure 1.

Indocyanine green angiography from a patient with confirmed West Nile virus infection. Late-phase indocyanine green angiograms of the (A) right eye and (B) left eye of a 58-year-old diabetic man with serologically confirmed West Nile virus infection show well-delineated hypofluorescent choroidal lesions that are more numerous than those appreciated by fluorescein angiography or clinically. Note the presence of a supramacular focal retinal arterial indocyanine green hyperfluorescence in the right eye. Reproduced with permission from.[66]

Figure 2.

Fundus photographs from a patient with confirmed West Nile virus infection. Fundus photographs of the (A) right eye and (B) left eye of the same patient as in Figure 1 demonstrating multiple chorioretinal lesions of various sizes that are partially atrophic and partially pigmented. Note the presence of nonproliferative diabetic retinopathy. Reproduced with permission from.[66]

Figure 3.

Fluorescein angiography from a patient with confirmed West Nile virus infection. Middle-phase fluorescein angiograms of the (A) right eye and (B) left eye of of the same patient as in Figure 1 show many more lesions that are observed clinically; these lesions are hypofluorescent centrally and hyperfluorescent peripherally. Reproduced with permission from.[66]

As indicated previously, patients may present with a range of ocular symptoms; however, it is important to note that most do not exhibit symptoms or display only a mild reduction in vision.[29,51,52,53,54,55,56,57,58,60,61,62] While most patients' vision eventually returns to baseline, the severity of their chorioretinitis certainly influences their outcome and recovery.[65] Diabetes has recently been shown to be a risk factor for the development of more severe chorioretinitis and as such, these patients have a worse prognosis.[68] Next, three cases of reported confirmed WNV associated chorioretinitis of varying severity are described; in addition, a case is described in which vitritis was the only ocular manifestation.

Case 1

Myers et al. reported the case of a 68-year-old female with severe vision loss due to extensive chorioretinitis.[65] The patient had a history of noninsulin-dependent diabetes, hypertension, congestive heart failure and coronary artery disease. She was hospitalized when her fever, clear nasal discharge, headache, myalgia, fatigue and dry cough persisted for several days. Her condition soon worsened and she began to experience a change in mental status. Upon ocular examination, her visual acuity was light perception ocular uterque (OU). Fundus examination revealed bilateral, multifocal chorioretinal lesions of variable sizes throughout the macula and mid-periphery. The vitreous was grossly clear and the optic discs were pink and flat. Multiple small intraretinal hemorrhages were observed OU, probably related to diabetic retinopathy as the patient had a history of diabetes. No treatment was given for the ocular symptoms. A total of 8 months later, the patient's health and mental status had recovered but visual acuity remained reduced to hand motions oculus dexter (OD) and light perception oculus sinister (OS). The appearance of her fundi had not changed.[65]

Case 2

Bains et al. reported the case of a patient with vitritis and chorioretinitis.[69] This 62-year-old female, with a 2-week history of floaters in her left eye, as well as fatigue, headache and low grade a fever, was found to have a visual acuity of 20/25 OD and 20/40 OS. Slit lamp examination revealed a few anterior vitreous cells OD and 2+ anterior cells OS. Ophthalmoscopy was significant with chorioretinal lesions measuring 500-750 µm in the left eye; similarly, less extensive lesions were seen in the right eye. Lesions were actively inflammatory and moderate vitritis was present in the superior retina of the left eye and overlying the optic disc. After 2 weeks the patient's vision improved to 20/30 OS, her vitritis improved and her floaters diminished.[69]

Case 3

Garg and Jampol discussed the case of a patient with chorioretinitis and long-term complications of subfoveal choroidal neovascularization.[29] The patient was a 73-year-old woman, with a history of well-controlled diabetes, who presented with fever, tremors, unintelligible speech, extreme lethargy and changes in mental status which developed a few days after the onset of fatigue. At 1 week postadmission with supportive care, the patient reported blurry vision in her right eye. Acuity OD was counting fingers (CF). Fluorescence angiography revealed numerous scattered white lesions ranging in size from 200 to 500 µm. After 3 months, her visual acuity improved to 20/60 OD. The authors suggested that a juxtafoveal chorioretinal lesion may have caused the severe decrease in vision and that its resolution over time led to improvement. After 18 months, the patient's visual acuity worsened again to CF OD due to the development of subfoveal choroidal neovascularization OD.[29]

Case 4

Yim et al. described an unusual case in which vitritis was the only ocular manifestation in a 9-year-old Caucasian girl with confirmed WNV infection.[70] She presented with decreased vision in her left eye that she had experienced since her initial diagnosis of acute otitis media and streptococcal pharyngitis 10 days earlier. Upon ophthalmic examination, the patient displayed visual acuities of 20/20 OD and 20/40 OS, with full visual fields and extraocular movements. Both of her anterior segments were normal. The posterior segment of her right eye revealed 1+ vitreous haze, 1+ vitreous cells with 2 snowballs, and a small infratemporal area of snowbanking. The vitreous of her left eye showed 2-3+ vitreous haze with 2-3+ cells with vitreous hemorrhage and possible snowbanking infratemporally. The patient was treated with 1 drop of 1% prednisolone acetate every 2 h and showed slow improvement with complete recovery of vision within 6 months.[70]


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