Zika virus infection

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

Epidemiology

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

Clinical presentation

In up to 80% of 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 also seen.

Radiographic features

Radiographic features of congenital Zika viral infection have 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 . 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.

History and etymology

The virus is named after the Zika (or Ziika) Forest (near Lake Victoria) in Uganda, as the virus was first isolated in a monkey at this location in 1947 .