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%) don’t cause symptoms. When symptoms do occur, they 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 usually develop from 3 to 12 days after being bitten by an infected mosquito.

It may be difficult to tell the difference between Zika symptoms and symptoms of other mosquito-borne infections such as dengue and chikungunya. Speak to your doctor about any symptoms you have following travel 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.

There is a theoretical risk of Zika transmission following transfusion of blood or a blood product collected from someone who was infected with the virus. The Australian Red Cross Blood Service currently requires donors who have travelled to countries with mosquito borne viruses such as dengue, malaria and Zika, to wait 4 months before donating blood.

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.

There is currently no known risk of Zika in Australia.

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:

• Cover up while outside (wear loose, long-sleeved, light-coloured clothing and covered footwear and socks). Mosquitoes can bite through tight clothing.
• Apply mosquito repellent evenly to all areas of exposed skin. The most effective repellents contain picaridin, DEET or oil of lemon eucalyptus. 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.
• The mosquitoes that transmit diseases such as dengue, chikungunya and Zika will bite all through the day
• Remove potential mosquito breeding sites from around the home
• Screen windows and doors
• Take extra precautions when travelling in areas with a higher risk of mosquito-borne diseases.

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 more information about:

• How to reduce the risk of mosquito bites at home and while overseas, read the Mosquitoes are a Health Hazard fact sheet. This includes more information on mosquito repellents.
• Going overseas, read the Staying healthy when travelling overseas fact sheet.
• If you are pregnant and choose to go to Zika-affected areas, consult your doctor or travel clinic for personalised mosquito prevention advice before you leave. You should strictly follow this advice when you are 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. Follow their advice.

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?

Laboratories notify their local public health unit when they confirm someone has Zika.

Public health units follow up each case to find out where the person may have got the infection. This information is important to help identify if transmission is occurring in areas considered to be low risk. It also aims to prevent transmission in areas of Australia that have the type of mosquito that can spread Zika virus.

For further information on the public health response please call your local public health unit on 1300 066 055.

If you have symptoms of Zika and you are concerned, speak to your doctor right away, or in an emergency call 000. For health advice you can also Healthdirect on 1800 022 222 for free 24-hour health advice or speak to your local pharmacist.