Zika virus

Zika is a primarily mosquito-borne virus that was first reported in a Rhesus macaque monkey in Uganda, 1947. This was followed by human infection and disease in other African countries in the 1950s. From the 1960s-80s, sporadic human infections were detected across Africa and Asia. Since 2007, outbreaks of Zika virus have been recorded in Africa, North and South America, Asia and the Pacific (World Health Organization (WHO), 2022).

In 2015, Zika caused an epidemic of unprecedented magnitude in the Americas, leading to the discovery of the teratogenic effects of Zika to the developing fetal brain (European Centre for Disease Control and Prevention (ECDC), 2023).

Zika virus can be transmitted from mother to fetus during pregnancy, as well as through sexual contact, transfusion of blood and blood products and possibly via organ transplantation (WHO, 2022).

Following a bite from an infected day-biting Aedes aegypti mosquito, the first symptoms of Zika can develop in around 3-12 days. Most people infected with Zika virus have no symptoms. For those with symptoms, Zika tends to cause mild, short-term illness lasting 2–7 days.

Symptoms can include:

• rash
• itching
• fever
• headache
• arthralgia (joint ache)
• myalgia (muscle ache)
• conjunctivitis
• lower back pain
• retro-orbital pain (Public Health England, 2017)

Following a particularly large epidemic of Zika virus in Brazil in 2015, an association between Zika infection and microcephaly (a birth defect in which a baby’s head is smaller than expected) was reported (WHO, 2022). From February-November 2016, following confirmation of the causal link between Zika infection in pregnancy and congenital malformations, the World Health Organization declared a public health emergency of international concern regarding microcephaly, other neurological disorders and Zika. Outbreaks of Zika were identified throughout most of the Americas and other regions with Aedes aegypti mosquitos. Sexual transmission was confirmed as an alternate route of infection following spread from travellers arriving from active transmission areas. Although Zika cases have declined worldwide since 2017, transmission persists at low levels in several countries in the Americas and other endemic regions. In 2021, most cases of Zika virus infection were reported in Brazil, Guatemala and Paraguay, with some new cases reported

Zika symptoms are similar to those of dengue (caused by a related flavivirus) or chikungunya (an alphavirus), which are often co-circulating in areas where Zika virus is present. Laboratory testing is essential for the correct diagnosis of Zika virus infection (Public Health England, 2017).

NHS testing for Zika virus is available only through the Rare and Imported Pathogens Laboratory (RIPL), part of the UK Health Security Agency. RIPL provides medical and laboratory specialist services to the NHS and other healthcare providers. Zika virus infection is not a notifiable disease in the UK, so there is no statutory requirement to test if the result will have no impact on clinical management (Public Health England, 2019a).

All travellers to countries where Zika is known to occur are at risk of infection, although it is difficult to determining the level of risk. Travellers who spend long periods of time in areas where Zika is common are at increased risk. However, even short-term visitors may be exposed to the virus (National Travel Health and Centre, 2022).

Pregnancy and travel

Zika virus infection in women who are pregnant or planning to get pregnant can result in serious birth defects. Although the probability of a fetus developing complications from Zika infection is low, the impact of these complications, should they occur, are very serious. UK travel advice, therefore, focusses on pregnant women, their partners and couples who are planning pregnancy (Public Health England, 2019b).

Before booking travel, pregnant women and couples considering pregnancy (within 3 months following travel) should check the Zika risk for their destination, using the UK Health

There is currently no vaccine or specific treatment available to prevent or treat Zika virus infection. Supportive care and relief of symptoms are the standard treatment for people infected with Zika virus (WHO, 2022). The best way to limit chances of Zika virus infection is to avoid mosquito bites, by using repellent, wearing clothing with more coverage or using mosquito nets.

People with symptoms such as rash, fever or joint pain should get plenty of rest, drink fluids and treat symptoms with antipyretics and/or analgesics. Non-steroidal anti-inflammatory drugs must be avoided until dengue infection is ruled out, because of the bleeding risk. If symptoms worsen, patients should seek medical care and advice. Pregnant women living in areas with Zika transmission or who develop symptoms of Zika virus infection should seek medical attention for laboratory testing, information, counselling and other clinical care (WHO, 2022).

Zika virus infection can cause Guillain–Barré syndrome, neuropathy and myelitis, particularly in adults and older children (WHO, 2022).