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The Zika virus: a brief update

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Dr Christine Chen
MBBS PhD FRANZCO
Head of Ophthalmology Department, Monash Health Melbourne

Dr Kira Michalova
MD FRANZCO
Medical retina specialist, NewVision Clinics Melbourne

 

The Rio Olympics are now over and the attention of the world has moved on but the threat of the Zika virus (ZIKV) remains. In this article, we present a very brief update on the Zika virus and its presumptive ocular associations, and provide some primary management guidelines.

The Zika virus is a single-stranded RNA Flavivirus. Other viruses in this family include the dengue fever virus and the yellow fever virus. ZIKV is transmitted by mosquitoes, especially the species named Aedes aegypti, but rare cases of sexual and vertical transmission have also been reported.1

Not a new virus

The Zika virus was first identified in Uganda in 1947 in macaque monkeys and then in humans in 1952.2 There have been subsequent outbreaks in tropical Africa, Southeast Asia and the Pacific Islands. More recently, the Zika virus has infected millions of Brazilians and is spreading rapidly throughout the Americas and into other parts of the world.

The Zika viral infection itself is rarely life-threatening, manifesting as a self-limiting non-specific viral illness with fever, non-specific rash, arthralgia and conjunctivitis, or it may be completely asymptomatic. However, a link has also been reported3 between Zika virus and a more severe illness, Guillain-Barre syndrome, a disease of the nervous system causing muscle weakness or paralysis.  

 

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Figure 1. Conjunctivitis in a case of imported Zika virus infection from French Polynesia to Japan, January 2014. Although the patient was afebrile upon examination, both bulbar conjunctivas appeared conjested.4

 

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Figure 2. Maculopapular rash on the back in a case of imported Zika virus infection from French Polynesia to Japan4

 

Recently, scientists from the American Center for Disease Control and Prevention (CDC) reported there is now enough evidence to conclude that Zika virus infection during pregnancy is a cause of microcephaly and other severe foetal brain defects and has been linked to problems in infants, including eye defects, hearing loss and impaired growth.

Scientists are studying the full range of other potential health problems that the Zika virus infection during pregnancy may cause. The World Health Organization has declared the Zika virus a ‘Public Health Emergency of International Concern.’

Currently, there is no commercial test available. To diagnose the Zika virus, the most important step is history-taking. Diagnostic testing includes a real-time reverse transcription-polymerase chain reaction (rRT-PCR) test which needs to be performed within the first 14 days of the infection. However, cross reaction with other Flaviviruses occurs. The more specific IgM test and neutralising antibodies test can take a few weeks.

Early this year, a Brazilian group published ocular findings in infants with microcephaly.5 The study, conducted over three weeks, examined 31 babies with microcephaly. The usual causes of congenital infection (toxoplasmosis, rubella, CMV, HSV, syphilis and HIV) were ruled out. Most of the mothers seemed to have signs and symptoms of a non-specific viral illness in the first trimester.

Of the babies with microcephaly, 10 (30 per cent) of the infants had ocular signs and a majority of these signs were bilateral. The examples of these were pigmentary mottling and chorioretinal atrophic lesions; some so severe they resembled coloboma. In some cases, the optic disc was involved with increased cup-to-disc ratio or optic disc hypoplasia.

 

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Figures 3A and 3B. Fundus photographs of a two-month-old girl. A: The right eye has granular, pigmentary mottling in the macula. B: The left eye has a chorioretinal lobulated atrophic lesion and slight pigmentary mottling.5

 

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Figures 4A and 4B. Fundus photographs of a four-month-old. Both right (A) and left (B) eyes have paramacular superotemporal round chorioretinal atrophy surrounded by a hyperpigmented halo and hyperpigmented mottling.5

 

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Figures 5A and 5B. Fundus photographs of a 20-day-old infant. A: The right eye has optic disc hypoplasia, peripapillary nasal atrophy and an excavated nasal round lesion with a hyperpigmented halo, with a colobomatous-like aspect. B: The left eye has optic disc hypoplasia, peripapillary nasal atrophy and a retinal nasal lesion with a similar pattern.5

 

Threat risk

In Australia, North Queensland harbours the vector mosquito and has had confirmed cases of Zika virus, but these appeared in people arriving from South America. No cases of local transmission have been reported in Australia.

The current recommendation is for all infants born with microcephaly in endemic areas to have an ophthalmic examination.

Pregnant women are advised not to travel to endemic areas. If women do travel to endemic areas, physical and chemical prevention of mosquito bites are recommended. If possible, pregnancy should be deferred for three months after travelling to endemic areas. Men in endemic areas should practise safe sex. Men with confirmed Zika virus infection should abstain from sex for three months.

If a pregnant woman who has recently travelled to an endemic area presents with conjunctivitis, she should be referred to her obstetrician for further management. The Royal Australian and New Zealand College of Obstetricians and Gynaecologists has issued guidelines on the care of women with confirmed Zika virus infection during pregnancy.6

This article is based on information currently available. Regular updates on Zika virus are available from the Australian Department of Health website, the Australian Smart Traveller website and the American CDC website. 

 

1.         Foy BD, Kobylinski KC, Chilson Foy JL, et al. Probable non-vector-borne transmission of Zika virus, Colorado, USA. Emerg Infect Dis 2011; 17: 5: 880-882.

2.         Dick GW, Kitchen SF, Haddow AJ. Zika virus, I: isolations and serological specificity. Trans R Soc Trop Med Hyg 1952; 46: 5: 509-520.

3.         Guillain-Barré Syndrome outbreak associated with Zika virus infection in French Polynesia: a case-control study. Van-Mai Cao-Lormeau, Alexandre Blake, Sandrine Mons, et al. Lancet 2016; 387: 1531-1539.

4.         Kutsuna S, Kato Y, Takasaki T, et al. Two cases of Zika fever imported from French Polynesia to Japan, December 2013 to January 2014. Euro Surveill 2014; 19: 4: 20694.

5.         de Paula Freitas B, de Oliveira Dias JR, Prazeres J, et al. Ocular findings in infants with microcephaly associated with presumed Zika virus congenital infection in Salvador, Brazil. JAMA Ophthalmol 2016; 134: 5: 529-535.

6.         The Royal Australian and New Zealand College of Obstetricians and Gynaecologists. Care of women with confirmed Zika virus infection during pregnancy in Australia. 18 Feb 2016 (accessed 20 July 2016). Available from: http://www.ranzcog.edu.au/images/Care_of_women_with_confirmed_zika_virus_infection_during_pregnancy_in_Australia.pdf



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