What is the current situation?
On 1 February 2016 the World Health Organization (WHO) declared a Public Health Emergency of International Concern related to the Zika virus outbreaks in many countries and, in particular, to the risk of congenital and other neurological disorders.
There is now international consensus that Zika virus infection is a cause of microcephaly and Guillain-Barré Syndrome (GBS).
Women who are pregnant or who are planning to become pregnant, should defer travel to areas with active local transmission of Zika virus .
WHO Zika Situation Reports provided regular situation updates. As of 13 July, WHO noted that 65 countries and territories had reported evidence of mosquito-borne Zika virus transmission since 2007, with 62 of these reporting evidence of mosquito-borne Zika virus transmission since 2015.
As of 13 July, WHO reported that microcephaly and other central nervous system (CNS) malformations potentially associated with Zika virus infection or suggestive of congenital infection had been reported by 13 countries or territories, including three countries with only imported cases. A total of 11 countries had reported evidence of person-to-person transmission of Zika virus, probably via a sexual route.
Where does Zika virus occur?
Zika virus occurs in tropical areas with large mosquito populations and is known to occur in Africa, the Americas, Southern Asia and the Western Pacific. Zika virus was discovered in 1947 in the Zika forest of Uganda, but for many years only sporadic human cases were detected in Africa and Southern Asia.
It first appeared in the Pacific in 2007 in a large outbreak on the island of Yap (Federated States of Micronesia). It re-emerged in the region with cases reported for the first time in French Polynesia in 2013-14, New Caledonia in 2014, and Cook Islands, Solomon Islands, Vanuatu, Fiji and Samoa in 2015.
Since 2014 there have been occasional cases of Zika virus notified in NSW in people who have acquired the infection while travelling overseas in areas with active transmission of the virus. With the explosive spread of Zika virus in the Americas and continuing outbreaks in the Pacific and Asia it is expected that more cases of infection will be identified in returned travellers.
What is Zika virus infection?
Zika virus infection is an illness caused by the Zika virus that is spread through the bite of infected mosquitoes. The virus is closely related to dengue virus and can cause a similar illness. The infection causes no symptoms in 80% of people but when it does the illness is usually mild and lasts 4-7 days. Symptoms of Zika virus infection arise 3-12 days after being bitten and may include fever, a rash, headache, red eyes, muscle aches, and joint pains.
There have been extensive epidemiological and laboratory studies of Zika virus complications and there is strong scientific consensus that Zika virus is a cause of microcephaly, GBS and may cause other congenital neurological disorders.
Who is at risk?
Travellers who go to affected areas in Africa, Asia, the Western Pacific and the Americas are at risk of getting Zika virus infection. The Aedes aegypti mosquito that is the main transmitter of Zika virus can bite during the day and night, both indoors and outdoors, and often lives around buildings in urban areas.
There is now substantial evidence that Zika virus can be transmitted sexually, although this seems to occur rarely. This of particular concern for pregnant women whose partners have returned from areas with local transmission of Zika virus.
How is it prevented?
Travellers to affected areas should avoid being bitten by mosquitoes. The Aedes aegypti mosquitoes that transmit Zika, dengue and chikungunya prefer to live and bite people indoors, and peak biting activity is during daylight hours. The mosquito hides under furniture and tends to bite around the feet and ankles. People may not notice they are being bitten.
Travellers to affected areas should stay in accommodation with screened windows and doors, wear loose fitting clothing that covers the arms and legs, and apply insect repellent containing DEET, picaridin, or oil of eucalyptus to exposed skin, especially during daylight hours and in the early evening.
For additional advice on steps to avoid being bitten by mosquitoes see the Mosquitoes are a Health Hazard Factsheet.
There is currently no vaccine against Zika virus.
For advice reducing the risk of sexual transmission of Zika virus during and following travel in affected countries see the NSW Health Zika virus factsheet and the Australian Department of Health Interim recommendations for reducing the risk of sexual transmission of Zika virus .
Will Zika virus spread in NSW?
It is very unlikely that Zika virus will establish local transmission in NSW as the mosquitoes that spread the infection overseas are not found here. There is no evidence that local mosquitoes can transmit the virus between people.
The Aedes aegypti mosquitoes that transmit Zika virus are found in some parts of north Queensland. This is why anyone diagnosed with Zika virus infection in NSW is advised against travel to north Queensland until they have cleared their infection from their bloodstream (usually about a week after their symptoms started).
Zika testing information for medical practitioners
In NSW, nucleic acid testing and serological testing for Zika virus infection is undertaken only in public health laboratories. Testing for Zika virus will usually be done concurrently with, or after excluding, other exotic infections with similar presentations - such as dengue, chikungunya, malaria, and measles - depending on travel history.
If Zika virus infection is suspected, clinicians are advised to discuss testing with their local pathology provider for information about appropriate tests, specimens to be collected and information to be provided on the request form (clinical history including date of symptom onset or date of last potential exposure if asymptomatic and travel history).