Zika Virus Infection

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Zika virus disease is caused by an RNA virus transmitted to humans by Aedes mosquitoes. The Zika virus is a flavivirus and is closely related to dengue virus, West Nile virus, yellow fever virus and Japanese encephalitis virus. Zika virus was first identified in rhesus monkeys in 1947 and recently there has been significant outbreaks in South East Asia, Pacific Islands and South America.

  • About 1 in 5 people infected with Zika virus become ill (i.e., develop Zika).
  • The most common symptoms of Zika are fever, rash, joint pain, or conjunctivitis (red eyes). Other common symptoms include muscle pain and headache. The incubation period (the time from exposure to symptoms) for Zika virus disease is not known, but is likely to be a few days to a week.
  • The illness is usually mild with symptoms lasting for several days to a week.
  • Zika virus usually remains in the blood of an infected person for a few days but it can be found longer in some people.
  • Zika virus has been detected in semen for several weeks post infection
  • Severe disease requiring hospitalization is uncommon.

Zika has not been noted to cause death in the past and neither has it been linked to intra-uterine infections and congenital CNS abnormalities. There has been a reported increase in congenital abnormalities in areas where Zika infection is occuring. However, the association of this with Zika virus is temporal and causality has yet to be proven.

Zika Virus Diagnosis

It is recommended to identify recent Zika infection by the detection of Zika virus RNA in blood, serum or urine samples. The current protocol stipulates the investigation of symptomatic patients who present within 2 weeks of onset of symptoms and who may have visited an area where Zika virus is circulating. For patients outside the 14 days testing is currently more problematic due to the unavailability of validated Zika specific IgM and IgG serological assays and the significant level of cross-reactivity observed in flavivirus assays due to dengue in particular.
The NVRL are currently validating a Zika RNA assay and anticipate that serological assays will be available for validation in the near future. In the short term if required the samples will be referred to the Rare and Imported pathogens Laboratory, Porton Down, UK for Zika investigation. If Zika infection is suspected based upon relevant travel history and symptoms, please contact Dr. Jeff Connell 01-716 1321 or clinical team 01-716 4418 to discuss the case and arrange investigation.