What is the current situation?
On 1 February 2016 the Director-General of the World Health Organization (WHO) declared that the recent cluster of microcephaly cases and other neurological disorders reported in Brazil, following a similar cluster in French Polynesia in 2014, constitutes a Public Health Emergency of International Concern.
Due to the concerns about the possibility of severe outcomes for unborn babies, women who are pregnant or who are planning to become pregnant, should consider delaying their travel to areas with active local transmission of Zika virus.
The WHO Zika situation report on 31 March 2016 noted that there were 42 countries experiencing a first outbreak of Zika virus, with no previous evidence of circulation, and with ongoing transmission by mosquitoes. Another six countries have had evidence of limited sexual transmission of Zika virus, with no evidence of mosquito-borne transmission.
In the Americas: 33 countries and territories have reported local transmission of Zika virus. No mosquito-borne transmission has been reported from the continental United States or Canada.
In the Pacific: Recent local transmission of Zika virus has been reported from American Samoa, Fiji, Marshall Islands, Samoa, Solomon Islands, Tonga and Vanuatu. Countries that have previously reported local Zika virus transmission include Cook Islands, French Polynesia, Federated States of Micronesia, New Caledonia, and Papua New Guinea.
Recent local transmission has also been reported from Cape Verde and the Maldives.
For up to date information see the list of Countries with current or recent active circulation of Zika virus compiled by the Australian Department of Health.
Where else 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, but for many years only sporadic human cases were detected in Africa and Southern Asia.
It first appeared in the Pacific in 2007 in 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, 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 it is expected that more cases of infection will be identified this year 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 often causes no symptoms 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.
Based on observational, cohort and case-control studies there is strong scientific consensus that Zika virus is a cause of Guillain-Barré syndrome (GBS), microcephaly and other neurological disorders.
Microcephaly and other fetal malformations have been reported in Brazil (944 cases), Cape Verde (two cases), Colombia (32 cases), French Polynesia (eight cases), Martinique (one case) and Panama (one case). Two additional cases, linked to a stay in Brazil, were detected in the United States of America and Slovenia.
In the context of Zika virus circulation, 13 countries or territories have reported an increased incidence of GBS and/or laboratory confirmation of a Zika virus infection among GBS cases.
Who is at risk?
Travellers who go to affected areas in Africa, Asia, the Western Pacific, and now the Americas are at risk of getting Zika virus infection (see US CDC Zika map). 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. See the Zika virus factsheet.
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 or picaridin 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 on the risk of sexual transmission of Zika virus following travel in affected countries see the Zika virus factsheet.
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.
Zika testing information for medical practitioners
In NSW, serological testing for Zika virus infection is undertaken only in the NSW Arbovirus Reference Laboratory at ICPMR - Pathology West (based at Westmead Hospital). 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).