Zika virus infection

Zika virus infection is a zoonosis which is associated with congenital birth defects, most famouslyinfamously microcephaly.

Epidemiology

Zika was once isolated to Africa and Asia, however, it spread to the Americas in the last decade ¹. There were thousands of cases confirmed in the Americas in 2018 ².

Clinical presentation

In up to 80% adult cases Zika disease is asymptomatic.When symptoms are present in adults, they are usually mild, with a similar presentation to dengue and chikungunya fever, including fever, malaise, joint pain and rash. Acute conjunctivitis and even rarely Guillain-Barré syndrome have been described.

Following vertical transmission to the fetus, the disease may be associated with congenital birth defects including microcephaly (and micrencephaly (small brain)).

Pathology

Zika is a single RNA stranded Flavivirus usually transmitted by a mosquito vector, for example Aedes aegypti.  Although both vertical and sexual virus transmission are seen ³.

Radiographic features

Radiographic features of congenital Zika viral infection hashave been reported on ultrasound, CT and MRI, and most result from a negative effect on brain development.

Congenital Zika has been shown to cause various brain abnormalities affecting both grey and white matter and ventricular size ^4,5. Intracranial calcifications resulting from congenital Zika virus infections are typically more florid than caused by the TORCH infections and also characteristically at the grey-white matter interface, which is unusual for other congenital viral diseases.

• brain
  • corpus callosum abnormalities, include hypoplasia, even agenesis
  • pontine atrophy
  • sharp angulation at the pontomedullary junction
  • hypoplastic cerebellum: hemispheric and/or vermian 
• spinal cord: decreased calibre with irregular morphology 
• orbit
  • asymmetric microphthalmia
  • cataracts
  • extension of the orbital fat into the cranial vault

Arthrogryposis is a commonly seen extracranial sequela.