WNV infection is an emerging disease worldwide and an endemic infection in Italy. In 2022, 586 cases of WNV infection were registered in Italy, representing 60,7% of the total human WNV infections in Europe [
9]. Emilia Romagna and Veneto, in north-eastern Italy, are the regions most affected by WNV infections. This condition depends mainly on native mosquitoes, the presence of susceptible endemic birds, and local environmental conditions [
2]. Moreover, human cases of WNV infection have consistently risen in Italy and Europe [
10].
In the present study, we describe the case of a patient who presented with bilateral multifocal chorioretinitis as the only presentation of acute West Nile virus infection, which required infectious disease consultation to rule out central nervous system involvement. Multifocal chorioretinitis is rare in patients with asymptomatic systemic infection. Chorioretinal involvement is mainly related to neuroinvasive cases, which are associated with high mortality, and a high risk of neurological complications. Hasbun et al. 2016 reported only one case of retinal involvement in 26 cases of asymptomatic WNV infection [
6]. In addition, Sanz et al. 2020 showed one case of unilateral chorioretinitis secondary to WNV infection in an asymptomatic patient with an eighteen-month history of photopsia and visual disturbances in her left eye [
7]. Multifocal chorioretinitis is the most frequent ocular manifestation of WNV infection. However, several ophthalmologic findings have been reported, including iridocyclitis, retinal vasculitis, macular edema, choroidal neovascularization, optic neuropathy, neuroretinitis, congenital chorioretinal scarring, ocular nerve palsy, and nystagmus secondary to encephalitis [
5,
11,
12]. Excluding the most severe cases, West Nile chorioretinitis is considered to be a self-limiting pathology if retinal and choroidal complications do not occur, and patients can be watched without treatment. Topical steroids and mydriatic agents can be used for anterior uveitis, while peripheral retinal photocoagulation of the ischemic areas of the retina can effectively prevent neovascularization. In addition, anti-vascular endothelial growth factor agents can be used to treat choroidal neovascularization, whereas surgical treatment can be required for vitreous hemorrhage or tractional retinal detachment [
12]. In cases of systemic involvement, there is no effective treatment for WNV infection, and supportive care remains the mainstay of treatment. The use of systemic steroids in WNV infections is controversial, and their utilization is reserved only in specific cases of potentially life-threatening neuroinvasive forms [
13]. Systemic steroid use carries the risk of elevating an immunosuppressive state, potentially exacerbating WNV viremia and worsening patient outcomes. Moreover, prior studies have not demonstrated a clear advantage of steroid treatment in cases of WNV encephalitis [
14]. However, recent experimental and clinical evidence suggests that pro-inflammatory mediators might play a role in WNV pathogenesis, and some case series have documented the administration of high-dose steroids leading to improved outcomes in patients with WNV neuroinvasive disease [
15]. Nonetheless, no randomized clinical trials have been conducted to assess the efficacy of systemic steroids in managing acute life-threatening infections and neurological sequelae in WNV infections, and there is no scientific evidence that support the role of systemic steroids in treating posterior uveitis, as WNV chorioretinitis typically follows a self-limiting course, with most patients regaining their baseline visual acuity
. Other endemic viruses can cause chorioretinal involvement. Post-fever retinitis is an infectious or para-infectious uveitic entity caused by several viral, or bacterial agents commonly seen in tropical countries. Ocular manifestations typically start developing within days to weeks after the onset of febrile illness, with different clinical features [
16,
17]. For instance, Rift Valley Fever virus can determine bilateral retinitis and occlusive vasculitis in the posterior pole, preceded by a fever in an endemic area [
18]. In the present case, the patient presented with pathognomonic linear lesions extending towards the periphery, following the retinal nerve fiber layer, suggestive of WNV infection. OCTA showed no evidence of superficial and deep retinal capillary ischemia, but attenuation of the choriocapillaris network at the lesion level. In 2017, Khairallah et al. described capillary rarefaction in the superficial and deep capillary plexus in a patient with occlusive retinal vasculitis associated with WNV infection [
19]. Our findings support the hypothesis of a primary location of disease activity at the level of the outer retina and RPE, with hematogenous spread of the virus via the choriocapillaris. We also observed granular hyperreflective specks located predominantly in the outer and inner nuclear layers, as previously described [
20].
To conclude, in the present case, we described the presence of bilateral multifocal chorioretinitis as the only presentation of acute WNV infection. Therefore, in endemic areas, it is crucial to consider WNV infection as an explanatory etiology in cases of multifocal chorioretinitis, even without neurological involvement.