Zika is a virus that is closely related to dengue. It is spread by mosquitoes. Zika virus was first found in 1947 and in Asia in 1969. However it may have been in these areas for much longer.
Zika virus was first reported outside Africa and Asia in 2007 where it caused an outbreak in Yap State (Federated States of Micronesia). Between 2013 and 2015 there were large outbreaks of Zika virus in the Pacific Islands, and in 2015, Zika virus emerged in South America, with spread to many countries in South and Central America and the Caribbean. Zika virus outbreaks are ongoing in the Americas and Pacific Islands.
Refer to the Department of Health webpage for the list of affected countries.
There is evidence of small numbers of cases of Zika virus reported in Southeast Asian countries such as Thailand, Papua New Guinea and Indonesia.
If someone is infected with Zika virus, it can typically take 3 to 12 days for symptoms to appear.
Approximately one person in five who catches Zika virus is likely to feel sick, and if they do, the disease is generally not severe and lasts only a few days. Symptoms may be similar to those caused by the flu and can include:
- a skin rash;
- pain in the joints;
- muscle pain;
- a headache, especially with pain behind the eyes;
- conjunctivitis (red eyes); and
- weakness or lack of energy.
Most people experience a very mild infection without any complications. However, recent outbreaks of Zika virus in the Pacific and the Americas show that Zika virus can be passed from a woman to her unborn baby. This can cause potentially serious consequences in the baby, in particular a condition called microcephaly (a small head and brain) and other birth defects.
There is also strong scientific agreement that Zika virus can cause a rare paralysing condition called Guillain-Barré Syndrome (GBS). This condition has been found in areas where Zika virus outbreaks are occurring and in cases of individual travellers returning from affected countries. GBS is known to be caused by other viruses and bacteria as well.
How it spreads
Zika virus is spread by the bite of a mosquito that is carrying the virus. Not all types of mosquitoes can spread it. Some types of Aedes mosquito can spread Zika virus, particularly Aedes aegypti but also possibly Aedes albopictus. Both are daytime biting mosquitoes, with increased activity around sunrise and sunset. Aedes aegypti mosquitoes often live in and around buildings in urban areas.
Most areas of Australia do not have the Aedes aegypti mosquito that can carry the virus. This mosquito is currently found in parts of Northern, Central and Southwest Queensland. Aedes albopictus is found in the Torres Strait Islands. Therefore, in most parts of Australia, there is no risk of Zika virus being spread by mosquitoes. Currently, all cases of Zika virus diagnosed in Australia were caught overseas.
Occasionally, Zika virus can also spread through sexual activity (vaginal, oral, or anal). However, the main way that Zika virus spreads is still by mosquitoes.
People at risk
People living in or visiting countries that are affected by Zika virus are at increased risk of Zika virus infection. Refer to the Department of Health page for a list of Zika virus affected countries.
High risk countries are currently experiencing widespread transmission of Zika virus. There is a high risk of travellers getting a Zika virus infection.
Moderate risk countries have sporadic cases of Zika virus infection occurring. Zika virus is present and may be reported in travellers, however it is not widespread, and the risk of travellers getting a Zika virus infection is thought to be lower than countries with widespread Zika virus.
Low risk countries have not recently reported Zika virus but it has been present in the past. There is a possibility of very low levels of Zika virus being present or occurring in the future. The risk is low but not zero.
Pregnant women should undertake an individual risk assessment with a doctor prior to making travel decisions. Pregnant women and their unborn babies are at particular risk of serious consequences of Zika virus infection. Preventing infection is essential. It is recommended that pregnant women or women planning a pregnancy defer travel to high risk countries. They should consider deferring travel to moderate risk countries. Travel to low risk countries by pregnant women can be considered following an individual risk assessment with a doctor. If they do decide to travel to a Zika-affected country, please see Preventing infection. Those planning pregnancy should defer pregnancy until at least 8 weeks after return. If their male partner is diagnosed with a Zika virus infection, pregnancy should be deferred for at least 6 months.
There is no vaccine for Zika virus infection. Prevention relies on avoiding being bitten by mosquitoes in countries where Zika virus occurs.Safe sex practices are also important in preventing sexual transmission.
How do I protect myself from mosquitoes?
All travellers should follow recommendations to avoid mosquito bites at all times when travelling in overseas countries where there is a risk of mosquito-borne diseases to reduce their risk of catching Zika virus. This is particularly important if you are pregnant or planning a pregnancy.
It is important to be aware that these precautions are necessary in the daytime and night time:
- Cover as much exposed skin as possible, including wearing light coloured long-sleeved shirts and long pants;
- Use insect repellents, applied according to the product label. The most effective mosquito repellents contain Diethyl Toluamide (DEET) or Picaridin. Repellents containing oil of lemon eucalyptus (OLE) (also known as Extract of Lemon Eucalyptus) or para menthane diol (PMD) also provide adequate protection. Note that insect repellents containing DEET or Picaridin, are safe for pregnant and breastfeeding women and children older than 2 months when used according to the product label. If you use both sunscreen and insect repellent, apply the sunscreen first and then the repellent;
- Use insecticide-treated (such as Permethrin) clothing and gear (such as boots, pants, socks, and tents); and
- Stay and sleep in screened-in or air-conditioned rooms. Use bed nets if you cannot keep mosquitoes from coming inside the room.
Seek medical advice, as soon as practicable, if unwell during or soon after travel.
How can sexual transmission of Zika virus be prevented?
Avoid unprotected sex while travelling in high or moderate risk a Zika virus affected country, and for at least 8 weeks after your return. This may be longer if an infection is diagnosed. Men or women who have travelled to a Zika virus affected country who have a pregnant partner should avoid unprotected sex (vaginal, oral, or anal) for the duration of the pregnancy. An individual risk assessment completed with your doctor can help you make decisions about what to do if you are unable to practice safe sex for 8 weeks after return from a Zika virus affected country.
Please see your doctor for further advice.
How Zika virus infection is diagnosed
A blood or urine test can diagnose Zika virus infection.
For further information on testing, please refer to Information on testing for Zika virus infection.
How Zika virus infection is treated
At the moment there is no specific treatment for Zika virus infection, but supportive medical care can be provided if required (e.g. rest, fluids).
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Preventing Zika virus spread in Australia
Health authorities prevent the spread of Zika virus in Australia by:
- In areas of Queensland where the mosquitoes Aedes aegypti and/or Aedes albopictus are present, health authorities will respond urgently to cases to prevent it from spreading in Australia, as they do for cases of dengue. This will include advising people on avoiding mosquito bites during their illness and may include controlling mosquitoes around the person’s home;
- Continuing to monitor international ports of entry to prevent the mosquitoes that can transmit Zika virus from entering or spreading to new areas; and
- Ensuring the safety of the blood supply through restrictions on whole blood donation for travellers coming to Australia from areas where mosquito-borne diseases are occurring.
What should I do if I think I might have Zika virus?
If you have returned within the last two weeks from travel to a Zika virus affected country and become unwell, you should see a doctor and mention your overseas travel.
All pregnant women who have travelled to a Zika virus affected country should see their doctor. Testing for Zika virus can be discussed depending on your individual risk assessment.
Women who have travelled to a high or moderate risk Zika virus affected country should not attempt to become pregnant for at least 8 weeks following the last day they were in a Zika virus affected country. Those who have travelled to low risk countries should have an individual risk assessment.
If you or your partner travelled to a Zika virus affected country, you may need to avoid unprotected sex (vaginal, oral, anal) for at least 8 weeks after your return. This may be longer if an infection is diagnosed. Men and women with a pregnant partner should avoid unprotected sex (vaginal, oral, or anal) for the duration of the pregnancy.
Can I still donate blood?
People who have been to Zika virus affected country should not donate whole blood for 4 weeks after they have returned.
If you are confirmed by a doctor to have Zika virus infection, you should not donate whole blood for 4 weeks after symptoms have disappeared.
If you have had had sex with someone who has been diagnosed with Zika virus infection at any time in the last 3 months, you should not donate whole blood for 4 weeks after the last time you had sex with that person.
Can I still donate sperm?
Men returning from Zika virus affected countries should wait at least 8 weeks upon return before donating sperm.
Men who have had a confirmed Zika virus infection should wait 6 months following diagnosis before donating sperm.
The Australian Government Department of Health website has the following resources that can provide more information:
If you have questions that are not answered by the above resources, or are unsure about any of the provided information, please consult your doctor.