What is Zika virus infection?

Zika virus infection (Zika) is caused by the Zika virus which is transmitted by certain types of Aedes mosquitoes. It can also be spread through sexual transmission, although this is rare.

Zika can cause the following conditions:

• rare congenital developmental malformations in babies born to mothers exposed to Zika during their pregnancy, including microcephaly (a condition where a baby’s head is smaller than expected and brain development can be impaired)
• rare neurological conditions, including Guillain-Barré Syndrome.

What are the symptoms of Zika virus infection?

Most infections (around 60-80%) will not cause symptoms. When symptoms occur, they usually develop from 3 to 12 days after being bitten by an infected mosquito. Symptoms are usually mild and last 4 to 7 days.

The main symptoms of Zika are:

• fever
• skin rash
• sore joints
• muscle pain
• headache
• conjunctivitis (inflamed eyes) is also common, usually without a discharge.

Symptoms of Zika may appear similar to symptoms of other mosquito-borne infections such as dengue and chikungunya. Speak to your doctor about any symptoms you have after travelling to areas affected by these mosquito-borne infections.

How is Zika virus spread?

Zika is mainly spread by the Aedes aegypti mosquito (the Dengue mosquito). It is possible that other mosquitoes in the Aedes family may also be able to spread the virus.

• People develop Zika after being bitten by a mosquito that is infected with the virus.
• The mosquito becomes infected when it bites somebody who has Zika virus in their blood.
• Once infected, the virus multiplies inside the mosquito and can infect other people when it bites them.

If a pregnant woman is infected with Zika, it can be passed to her baby.

Sexual transmission has also been reported, though this is rare.

Who is at risk of getting Zika virus infection?

People who travel to Zika affected areas, such as Africa, Asia, the Western Pacific and the Americas, are at risk of getting Zika. See the United States Centers for Disease Control and Prevention website for a map showing the risk of Zika transmission in different countries.

The sexual partners of people who have been infected with Zika while travelling overseas are also at risk.

Due to the concerns about the risk of severe outcomes for unborn babies, women who are pregnant or planning to become pregnant should consider delaying their travel to areas with active outbreaks of Zika.

How is Zika virus infection prevented?

There is currently no vaccine against Zika.

Protect yourself against mosquitoes and the risk of diseases they transmit:

• Wear light-coloured, long-sleeved shirts, long trousers and enclosed shoes. Mosquitoes can bite through tight clothing.
• Apply mosquito repellent containing picaridin, DEET or oil of lemon eucalyptus, evenly to all areas of exposed skin. Natural or homemade repellents provide limited protection. Read the instructions to find out how often you should reapply repellent. Always apply sunscreen first and then apply repellent.
• Take special care during peak mosquito biting hours. 
• Remove stagnant water around the home as they can become mosquito breeding sites.
• Use mosquito nets, and screen windows and doors.

In addition to the general protection measures above, overseas travellers should also:

• Stay and sleep in screened or air-conditioned rooms
• Use a bed net if the area where you are sleeping is exposed to the outdoors. Nets are most effective when they are treated with a pyrethroid insecticide, such as permethrin. Pre-treated bed nets can be purchased before travelling, or nets can be treated after purchase.
• Avoid known areas of high mosquito-borne disease transmission or outbreaks.

For mosquito bite prevention information, see Mosquitoes are a health hazard and Staying safe and healthy overseas.

Preventing Zika virus infection in pregnancy

Zika may cause severe birth defects. Pregnant women should avoid travel to countries with active Zika outbreaks and reconsider travel to countries with past Zika outbreaks. For information on Zika activity by country, see the United States Centers for Disease Control and Prevention website.

If you are pregnant or considering pregnancy, talk to your doctor about the risk of Zika in the country you are travelling to. You should strictly follow this advice when you are overseas.

How is Zika virus infection diagnosed?

Your doctor can take a blood sample and have it tested for the virus (if in early stages of the illness), or antibodies against Zika virus. A second blood test taken two weeks later may be required to confirm a recent infection.

How is Zika virus infection treated?

There is no specific treatment for Zika. Your doctor can give you advice on how to treat any symptoms with medications such as paracetamol.

Treatment with aspirin or ibuprofen is not recommended because of:

• a potential increased risk of haemorrhagic syndrome (bleeding) reported with some related viruses, such as dengue, and
• the risk of a rare but serious illness called Reye’s syndrome after viral infection in children and teenagers.

Pregnant women with Zika will be referred for specialist obstetric assessment for advice on the monitoring of their baby.

What is the public health response to Zika virus infection?

If you have symptoms of Zika and you are concerned, speak to your doctor right away, or in an emergency call 000.