What is Zika virus?
Zika virus is a mosquito-borne virus passed from an infected person to another person through the bite of a female Aedes mosquito. Originally isolated in 1947 in a monkey from a Ugandan forest, the Zika virus (ZIKV) wasn’t seen in humans until several years later. Since 2007 ZIKV disease outbreaks have become more frequent and of a larger scale: Africa was first affected and more recently Asia, Pacific, Caribbean and the Americas.
The mosquitoes that transmit Zika virus are also the main vectors for dengue fever and chikungunya; they are usually found near human habitation and are active during daylight hours – dawn and dusk are the peak feeding times. They are found in most tropical and sub-tropical regions of the world so the risk of further spread of the virus to unaffected countries is real.
Many people suffering infection with Zika virus will show no symptoms – around 1-in-5 will develop Zika virus disease (ZVD). Symptoms are similar to those of dengue fever: headache, fever, joint pain, and rash. Unlike dengue, sore, red eyes from conjunctivitis is common in ZVD. In most cases symptoms resolve in under a week and severe disease is rare: there have been several reports of a potentially severe autoimmune disease, Guillain-Barré syndrome, following ZIKV infection.
A diagnosis is made through blood testing and because of the similarity of the symptoms to dengue and chikungunya, these must be excluded.
Transmission of Zika virus has occurred during pregnancy, breastfeeding, sexually and also through blood transfusions. The incidence of microcephaly in newborn infants has increased markedly in areas reporting ZIKV outbreaks leading to concerns of a causal association between the two. Microcephaly is a neurodevelopmental disorder that leads to babies being born with smaller heads. The infant’s brain is underdeveloped, causing both intellectual and motor disabilities
There is no vaccine available to prevent infection with Zika virus and travellers heading to risk areas are advised to use strict measures to avoid mosquito bites. These include:
- Wear protective clothing – long sleeves and long trousers/skirt
- Apply insect repellent containing DEET, Picaridin or Citriodiol or PMD to exposed skin.
- Use aerosol insecticides indoors.
- Sleep under a mosquito net if not in well-screened or air-conditioned accommodation.
- Use Permethrin to impregnate nets and clothing.
- Eliminate any standing water around dwelling.
- Pregnant women (in any trimester) or those planning pregnancy are advised to reconsider the need for travel to affected /outbreak regions. If travel is unavoidable, strict mosquito bite prevention measures must be followed.
- Information on Zika virus and links to sites containing more detail, such as the WHO and US CDC, are available through the Department of Foreign Affairs and Trade website, smartraveller. It is also recommended to subscribe to their travel advisory updates for any further developments in the situation. https://smartraveller.gov.au/accounts
As there is no specific cure for Zika virus infection; treatment is usually supportive and includes rest, fluids and pain relief. Non-steroidal anti-inflammatory medications should not be used until dengue fever has been excluded in the diagnosis. Exposure to mosquito bites must be avoided during the first few days of illness to reduce the risk of further transmission of the virus.