Features

The Zika virus belongs to the genus of viruses in the family Flaviviridae, which also includes West Nile, dengue, and yellow fever. These viruses are composed of positive-sense single-stranded RNA enveloped in an icosahedral nucleocapsid. The most common mode of transmission is from the bite of an infected arthropod (e.g., Aedes aegypti and Aedes albopictus mosquito species) that is endemic to tropical and temperate climate regions. There have also been documented cases of transmission sexually, congenitally, and through blood transfusion and organ transplantation. Furthermore, the virus has recently been detected in other bodily fluids, raising the possibility of potential transmission through nonsexual contact.

Studies have found that infection during the first trimester is linked to the development of microcephaly. While the understanding of the pathophysiology of microcephaly associated with congenital Zika virus infections (CZI) has made tremendous progress, the association of CZI with chorioretinal maculopathy is less well understood. While some believe Zika virus to be the direct cause, these findings may be sequelae of Zika-induced microcephaly. Microcephaly itself has been shown to be associated with chorioretinal degeneration, pigmentary changes, and vascular abnormalities. Thus, it is important to investigate the mechanisms for these findings so as to properly attribute the pathophysiology.

61.1.1 Common Symptoms

Ocular

Vision-threatening fundus abnormalities in infants with CZI. Eye redness in adults.

Systemic

Varies from asymptomatic to mild symptoms, including fever, rash, and joint pain.

61.1.2 Exam Findings

Chorioretinal atrophy and pigment mottling may be present.

61.2 Key Diagnostic Tests and Findings

61.2.1 Serology

The recent development of a serologic test for an immunoglobulin M (IgM) antibody to the virus has improved the screening process. The IgM antibody develops within 1 week after infection and can stay positive for up to 12 weeks afterward. This method has been recommended as a screening method for neonates suspected of having CZI; however, its low specificity and high cross-reactivity to other flaviviruses pose significant challenges. A positive result requires a confirmatory plaque reduction neutralization test performed at the Centers for Disease Control and Prevention (CDC). Furthermore, microcephaly is no longer a required criterion for screening neonates.

61.2.2 Fundus Photography

Possible focal pigment mottling and chorioretinal atrophy (▶ Fig. 61.1). To date, limited diagnostic evaluation of retinal findings has been described such as optical coherence tomography and angiography due to the challenging issues related to examination, including the frequent necessity of performing the exam under anesthesia.

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