Zika Virus Infection

Zika virus infection is an arboviral infection caused by Zika virus, a flavivirus transmitted predominantly by Aedes species mosquitoes. Additional recognised transmission occurs through sexual contact and, importantly, vertically from mother to fetus.

It produces a generally mild, self limiting febrile illness in the great majority of infected adults.

The overwhelming clinical significance of this infection derives from its capacity to cause severe congenital abnormalities, principally microcephaly and other significant neurodevelopmental consequences, following maternal infection during pregnancy.

Prevention of infection during pregnancy and appropriate counselling of pregnant women are therefore the central clinical priority for this condition.

Pathophysiology and transmission

• Following mosquito borne transmission, the virus produces a generally mild systemic illness in the majority of infected adults.
• The virus is additionally capable of persisting in semen for an extended period following acute infection, underlying the recognised sexual transmission route.
• It can also cross the placenta to directly infect fetal neural progenitor cells. This specific neurotropism for developing neural tissue explains the severe congenital neurological consequences of intrauterine infection, particularly when acquired during the first and early second trimester.
• Guillain Barré syndrome is a recognised, though uncommon, post infectious complication in adults, reflecting a similar immune mediated mechanism to that seen following other antecedent infections.

• The majority of infections (estimated at around eighty percent) are asymptomatic.
• Symptomatic disease presents as a mild illness comprising low grade fever, maculopapular rash, conjunctivitis (typically non purulent), arthralgia and myalgia. It generally resolves within a week without specific treatment.
• Congenital Zika syndrome results from maternal infection during pregnancy. It encompasses microcephaly (often severe), other significant structural brain abnormalities (including intracranial calcification and ventriculomegaly), ophthalmological abnormalities, congenital contractures, and significant neurodevelopmental impairment.
• Severity and risk are generally greatest with maternal infection during the first trimester, though risk persists, at a somewhat reduced level, throughout pregnancy.
• Guillain Barré syndrome, presenting with the typical ascending flaccid paralysis pattern, can follow Zika virus infection by one to two weeks. This mirrors the post infectious pattern recognised following various other antecedent infections.
• Specifically seek a relevant travel history to an endemic or currently affected region. Also ask about sexual contact with a partner who has travelled to or resides in such a region. This is particularly urgent in any pregnant woman with a compatible illness or relevant exposure risk.

• Polymerase chain reaction testing on blood and urine offers the most sensitive diagnostic approach during the acute phase of illness, generally within the first one to two weeks after symptom onset. Urine testing offers a somewhat longer window of detectable viral shedding compared with blood.
• Serological testing (IgM antibody detection) is used beyond the acute window. Cross reactivity with other flaviviruses can complicate interpretation, particularly dengue, given frequently overlapping geographical distribution and prior exposure in endemic populations.
• More specific confirmatory testing (plaque reduction neutralisation testing) at a specialist reference laboratory is sometimes required.
• Pregnant women with a relevant exposure history or compatible symptoms require specific testing following relevant national or regional guidance. They also require serial fetal ultrasound assessment to monitor for structural abnormalities suggestive of congenital infection.
• Where infection is confirmed or the fetal ultrasound is suggestive, refer to specialist maternal fetal medicine services for detailed assessment and counselling.
• Postnatal assessment of an infant with suspected congenital Zika exposure includes clinical examination (head circumference, neurological assessment) and cranial imaging. Where indicated, add ophthalmological and audiological assessment, given the recognised spectrum of congenital abnormalities associated with this infection.

• Management of acute, uncomplicated Zika virus infection in a non pregnant adult is entirely supportive.
• Paracetamol is preferred over nonsteroidal anti inflammatory drugs and aspirin for symptomatic relief until dengue coinfection or an alternative diagnosis has been reasonably excluded. This reflects the overlapping geographical distribution and clinical presentation with dengue and the associated bleeding risk considerations relevant to that condition.
• There is no specific antiviral treatment available for Zika virus infection, and no currently licensed vaccine. Prevention relies entirely on mosquito bite avoidance and, given the recognised sexual transmission route, appropriate barrier contraception advice.
• Pregnant women are specifically advised to avoid travel to regions with active Zika virus transmission wherever possible.
• Where travel cannot be avoided or where a partner has relevant travel exposure, advise rigorous mosquito bite avoidance measures and barrier contraception for a defined period following any potential exposure, according to current public health guidance. This reflects the risk of sexual transmission from an infected partner.
• Confirmed or suspected congenital Zika syndrome requires full, multidisciplinary paediatric assessment and long term follow up, including neurodevelopmental surveillance. Manage any specific identified complications: seizure management where relevant, physiotherapy and occupational therapy support, and ophthalmological and audiological intervention as indicated.
• Deliver this care through a coordinated specialist paediatric service, given the complex, multisystem nature of this condition.
• Guillain Barré syndrome following Zika virus infection is managed according to standard treatment principles for this condition. These are intravenous immunoglobulin or plasma exchange, together with supportive respiratory monitoring given the risk of respiratory muscle involvement.
• The approach is the same as for Guillain Barré syndrome regardless of the specific preceding infective trigger.
• Public health notification and, where relevant, vector control measures in affected regions form part of the broader public health response to this infection. It has significant public health importance, particularly regarding the devastating congenital consequences of maternal infection during pregnancy.