Zika virus

About Zika virus

Zika virus (ZIKV) infection is a mosquito-borne disease, transmitted by bites from some species of Aedes mosquito, particularly Aedes aegypti. These mosquitoes usually bite during the day, particularly around dawn and dusk.

People with Zika virus usually have no symptoms, but around 20% of people infected with Zika virus get symptoms of fever, rash, itchy red eyes (conjunctivitis), headache, joint and muscle pain.

Illness from Zika virus is usually not severe and does not normally require hospitalisation.

In rare cases, Zika virus infections can lead to Guillain-Barre syndrome, a neurological disorder.

Infection with Zika virus in pregnancy can result in miscarriage, stillbirth or serious birth defects in the newborn, including microcephaly (abnormally small head and brain).

Outbreaks of Zika virus have occurred in Africa, the Americas, Asia, Europe and the Pacific. All cases of Zika virus detected in Australia have been in travellers returning from overseas.

There is no specific treatment or vaccine currently available. The best form of prevention is to avoid being bitten by mosquitoes, and using condoms or not having sex if you are in a country currently affected by Zika virus.

History of Zika virus

Zika virus was first identified in Uganda in 1947 in monkeys.

The first human cases were detected in 1952.

Numerous outbreaks of Zika virus have been reported around the world since 2007.

In 2015 and 2016 a large outbreak beginning in Brazil spread to neighbouring regions, leading to the World Health Organization declaring a global health emergency. This outbreak has since declined, however smaller outbreaks are still regularly detected in various countries worldwide.

Symptoms of Zika virus

Symptoms usually develop within 2 weeks of someone being exposed to Zika virus. Most people do not develop symptoms. When symptoms are present, they are usually mild and can last from a few days up to a week.

Symptoms can include:

• fever
• skin rashes
• conjunctivitis (red eyes)
• headache
• muscle and joint pain.

Zika virus complications

Guillain-Barré syndrome (GBS), a rare neurological disorder, has been linked to Zika virus infection in some cases. GBS is an illness where a person's own immune system damages their nerve cells, causing muscle weakness and sometimes paralysis.

Zika virus can also rarely cause inflammation and swelling of the brain (encephalitis), tissues around the brain (meningitis), or spinal cord (myelitis). It can also cause a blood disorder that results in bruising, bleeding or slow blood clotting.

Zika virus infection during pregnancy can lead to severe birth defects, including microcephaly (abnormally small head and brain) in newborns.

Spread of infection

Zika virus is usually transmitted to people through the bite of an infected mosquito from the Aedes genus, mainly Aedes aegypti. This is the same mosquito that transmits the viral infections dengue, chikungunya and yellow fever.

Zika can also be transmitted:

• through sexual contact
• from mother to child during pregnancy
• rarely via blood transfusion or organ transplants.

To reduce the risk of transmitting Zika virus via transfusion of blood or blood products, the Australian Red Cross LifeBlood currently requires donors who have travelled to countries with mosquito borne viruses such as Zika, dengue and malaria to wait before donating blood. For more information, see Blood testing and safety.

Diagnosis of Zika virus

Zika virus infection is diagnosed through:

• medical history, including a travel history to look for any exposure in a country with active Zika transmission in the 2 weeks prior to illness
• physical examination to look for evidence of the infection
• blood and other laboratory tests.

Treatment for Zika virus

Zika virus disease is usually relatively mild.

Currently, there is no cure or specific treatment for Zika virus. Treatment aims to ease symptoms and reduce the risk of complications while the person recovers.

People diagnosed with Zika virus infection should:

• get plenty of rest
• drink enough fluids
• treat pain and fever with common medicines such as paracetamol.

Do not take aspirin or other non-steroidal anti-inflammatory drugs (such as ibuprofen) unless advised by your doctor.

If you have visited a country with active Zika virus transmission and have symptoms that could be caused by Zika infection, you should seek medical care and advice, especially as there could be other causes of your symptoms.

If symptoms worsen, seek further medical care and advice.

Prevention of Zika virus

There is currently no vaccine available to protect against Zika virus.

All travellers planning to visit areas that are currently or potentially affected by Zika virus should take the following measures to prevent mosquito bites:

• Wear light-coloured, long-sleeved shirts, long pants and enclosed shoes. Mosquitoes can bite through tight clothes.
• Use insect repellents containing DEET or picaridin. Always use as directed. Insect repellents containing DEET and picaridin are safe for pregnant and breastfeeding people and children older than 2 months when used according to the product label.
• Use permethrin-treated clothing and gear (such as boots, pants, socks, and tents).
• Stay and sleep in screened-in or air-conditioned rooms. Sleep under a mosquito bed net if accommodation is not screened-in or air-conditioned rooms are not available.
• Remove stagnant water around the home (such as containers, pots or buckets) as they can become mosquito breeding sites.

The Australian Government's Smartraveller website has important travel advice for pregnant people, people trying to get pregnant and other travellers.

Prevention of sexual transmission

Pregnant people and people trying to get pregnant, as well as their sexual partners, should consider deferring non-essential travel to areas with active Zika virus transmission.

People travelling to areas with Zika transmission should consider using condoms or not having sex while travelling and for a period of time after returning home, to avoid transmitting Zika virus. This is especially important for male partners of people who are pregnant or trying to get pregnant.

For males returning from a Zika-affected country:

• Do not have sex (vaginal, anal, or oral, as well as sharing sex toys), or consistently use condoms for at least 3 months upon return.
• Wait for at least 3 months before donating sperm.

For females returning from a Zika-affected country:

• Do not have sex (vaginal, anal, or oral, as well as sharing sex toys), or consistently use condoms for at least 2 months upon return.

For males who are diagnosed with Zika:

• Do not have sex (vaginal, anal, or oral, as well as sharing sex toys), or consistently use condoms for at least 3 months from the onset of symptoms or date of Zika diagnosis (for asymptomatic cases).
• Wait for at least 3 months before donating sperm.

For females who are diagnosed with Zika:

• Do not have sex (vaginal, anal, or oral, as well as sharing sex toys), or consistently use condoms for at least 2 months from the onset of symptoms or date of Zika diagnosis (for asymptomatic cases).

For males with a pregnant partner, it is particularly important to follow the above recommendations. Males with a pregnant partner should not have sex or consistently use condoms for the duration of the pregnancy or for at least 3 months after they were last in the at-risk country or diagnosed, whichever is longer.

Always discuss your individual risk with your doctor.

Which countries are affected by Zika virus?

The most up-to-date information on countries experiencing active Zika virus transmission is available on the Smartraveller website.

People planning travel are advised to check whether the country they are planning to visit has active Zika virus transmission.

The mosquito species that can carry Zika virus are found in parts of northern Queensland. However, no-one is known to have been infected with Zika virus within Australia.

Where to get help

• Your GP (doctor)
• Your Local Public Health Unit
• Zika virus infection, Department of Health
• Zika virus, Healthdirect Australia