- Zika virus areas of risk
- Advice for travellers
- About Zika virus
- Symptoms and signs of Zika virus infection
- Complications of Zika virus infection
- Laboratory testing
- Blood Donation
- Public health management of a laboratory confirmed case
- Further information is available
- Summary table of recommendations regarding Zika virus prevention
Zika virus infection is generally a non-severe febrile viral illness transmitted by mosquitoes. Zika virus infection should be considered in people who have recently travelled overseas.
Scientific evidence from outbreaks of Zika virus shows that a Zika virus infection in a pregnant woman can be transmitted to the fetus, and can cause certain congenital abnormalities (including microcephaly). Further studies are required to understand the degree of risk of an adverse outcome occurring and the factors that influence this risk.
Specific travel precautions are recommended for pregnant women or women planning pregnancy who are travelling to a Zika area of risk.
The United States Centers for Disease Control and Prevention (CDC) Zika Travel Information webpage provides up-to-date travel recommendations for Zika by country and traveller type.
For more information and to access the CDC Zika Travel Information webpage.
A note on altitude in considering countries
The mosquitoes that spread Zika virus do not usually live at elevations above 2000 metres. Travellers who plan to only be in areas above this elevation are at very low risk. Pregnant travellers should be aware of changes to travel plans that take them to lower elevations. Areas of low likelihood of Zika infection, because of elevation above 2000 metres, are identified on the CDC Zika Travel Information page.
Refer to the table Summary table of recommendations regarding Zika virus prevention .
All travellers are advised to undertake a pre-travel risk assessment with their doctor.
No vaccine is available for Zika virus.
All travellers should be advised on mosquito bite avoidance and safe sex measures. Refer to the section on Prevention.
Pre-travel advice for pregnant women
Zika virus infection in a pregnant woman may cause severe birth defects. Pregnant women should consider deferring travel to a Zika affected country. An individual risk assessment is advised for women considering travel to a country where there is the potential for Zika transmission. If the woman does decide to travel, discussion with a doctor about preventing Zika virus transmission from mosquitoes and sexual partners is advised.
Women planning a pregnancy or at risk of pregnancy should either consider deferring travel as described above, or avoid pregnancy during travel and for at least 8 weeks afterwards.
Post exposure advice for pregnant women
Protecting pregnant women or those planning pregnancy is a priority. Pregnant women should avoid unprotected sex with partners who have been to a Zika area of risk for the duration of the pregnancy. Refer to the CDC Zika Travel Information page for post travel advice for pregnant women.
Post exposure advice for other travellers
Testing is recommended for all people who have signs or symptoms of potential Zika virus infection. Testing may also be considered in couples planning pregnancy who have been exposed to Zika. Refer to the section on Laboratory testing, and seek advice from a pathologist on sample type and timing if testing is requested.
Refer to the CDC Zika Travel Information page for post travel advice for other travellers.
All men and women should follow the recommendations for prevention of sexual transmission that are relevant to their circumstances, refer to Prevention and Summary table of recommendations regarding Zika prevention.
Travellers returning to areas of Queensland with suitable mosquitoes to transmit Zika should avoid mosquito bites for 3 weeks after return. Advice to travellers returning from a country where there is the potential for Zika transmission should be based on an individual risk assessment.
Zika virus is a flavivirus, closely related to Dengue virus. It is transmitted to humans primarily through the bite of certain infected Aedesspecies mosquitoes. Aedes aegypti mosquitoes are commonly found in tropical and sub-tropical regions around the world including North Queensland and some areas in Central and Southwest Queensland. Another similar mosquito, Aedes albopictus, also has the potential to transmit Zika virus, but in Australia is only found in the Torres Strait.
Outbreaks of Zika virus have previously been reported in tropical Africa, Southeast Asia, and the Pacific Islands.1 In 2015, Zika virus emerged in South America with widespread outbreaks reported initially in Brazil and Columbia,2, 3 with spread to many countries in South and Central America and the Caribbean.4
Zika virus is transmitted to humans primarily through the bite of infective Aedes mosquitoes, most commonly Aedes aegypti. This is the most important mode of transmission.
Multiple instances of probable or confirmed sexual transmission have now been reported, and to date, almost all have involved a symptomatic man transmitting the Zika virus to a woman,5, 6, 7, 8 but female-to-male and male-to-male transmission has also been reported.9, 10 From these cases, it is known that the sexual transmission can occur before, during, or after symptoms. There has been one case of likely sexual transmission from an asymptomatic male.11
The longest reported period between symptom onset and sexual transmission is 32-41 days (based on an incubation period of 3-12 days).12 Zika virus RNA has also been found in the semen of five men more than 90 days after onset, and in one (1) case up to 188 days after onset of infection13,14, 15, 16 Viral RNA has been detected in the genital tract of one women on day 11, and another up to day 13, and was cleared by day 17 in both women.17, 18
To date, there are no reports of infants becoming infected through breastfeeding. The World Health Organization recommends that breastfeeding continues, with benefits for the infant and mother outweighing any potential risk of Zika virus transmission through breast milk.19
Zika virus RNA can be detected in serum usually for a few days to a week. Refer to Blood Donation
Current recommendations are cautious, as evidence about transmission is still emerging.top of page
Approximately one person in five who becomes infected with Zika virus is likely to have symptoms.20 For cases with a clinical illness, symptoms may include one or more of:
- Low-grade fever
- Maculopapular rash
- Arthralgia, notably of small joints of hands and feet, with possible swollen joints
- Headache, retro-ocular headaches
- Post-infection fatigue
More rarely observed symptoms include digestive problems (abdominal pain, diarrhoea, and constipation), mucous membrane ulcerations (aphthae), and pruritus.
Zika virus infection generally causes a non-severe disease. However it does have the potential to cause congenital abnormalities of the fetus in pregnant women, and the chance of Guillain-Barré Syndrome (GBS), which are discussed below. As Zika virus infection may cause a rash that could be confused with other diseases such as measles or dengue, these diseases need to be ruled out.
The incubation period is typically 3–12 days. Acute symptoms typically resolve within 4–7 days.
Pregnant women who become infected with Zika virus can transmit the infection to their unborn babies, with potentially serious consequences including microcephaly and a range of other abnormalities that may be present at birth or develop in infancy, known as congenital Zika virus syndrome (CZVS).21, 22, 23, 24 Based on current evidence, the risk of congenital abnormalities appears to relate to all trimesters of pregnancy.25, 26, 27 A small number of studies are available on the frequency of congenital defects in babies exposed to Zika in-utero. The most recent is a study of 972 completed pregnancies from the U.S. Zika Pregnancy Registry, where 5% of babies born to women with possible Zika infection during pregnancy showed evidence of congenital abnormalities, while 10% of births to mothers with confirmed Zika infection showed evidence of congenital abnormalities.28 Where the confirmed infection in the mother occurred in the first trimester, the proportion of babies with congenital abnormalities was higher (15%). A meta-analysis of eight cohort studies of pregnant women infected with Zika estimated the prevalence of microcephaly as 2.3% (95% CI=1.0—5.3) of live births to Zika-infected women, with individual study prevalences ranging from 0% to 11%.29 A recent study of Zika Virus associated neonatal birth defects in Texas (following the outbreak that occurred there) showed that 8% (15 births) had any kind of Zika-associated birth defect, and 5% (10 births) had microcephaly.30
For guidance on assessing pregnant women returning from an area at risk of Zika virus, refer to the interim recommendations for assessment of pregnant women returning from Zika affected countries.
Further information on management of a pregnant woman who has had a positive Zika virus test is available in the RANZCOG guideline, Care of women with confirmed Zika virus infection during pregnancy in Australia.
Several countries that have experienced Zika virus outbreaks have reported increases in the number of people who have GBS. Research suggests that GBS is associated with Zika virus,28 however only a small proportion of people with recent Zika virus infection get GBS.
It is to be noted that GBS is a known complication of a number of infectious diseases including Campylobacter spp., influenza virus, Epstein - Barr virus, HIV and Mycoplasma pneumoniae. In addition, GBS can occur following surgery or in those with Hodgkin’s lymphoma. In rare cases it can be life-threatening in the absence of appropriate care.
Refer to the CDC website for further details.
Based on the typical clinical features, the differential diagnosis for Zika virus infection is broad. In addition to dengue, other considerations include leptospirosis, malaria, rickettsia, group A Streptococcus, rubella, measles, and parvovirus, enterovirus, adenovirus, and alphavirus infections (e.g., Chikungunya, Mayaro, Ross River, Barmah Forest, O’nyong-nyong, and Sindbis viruses).
Preliminary diagnosis is based on the patient’s clinical features, places and dates of travel, and activities. Laboratory diagnosis is generally accomplished by testing serum or plasma to detect virus, viral nucleic acid, or virus-specific immunoglobulin M and neutralising antibodies.top of page
Zika virus testing is performed at state public health laboratories in Australia. If Zika virus infection is suspected, clinicians are advised to discuss testing with their local pathology provider.
Testing for Zika virus may include IgM, IgG serology and PCR performed on blood, urine, amniotic fluid, cerebrospinal fluid or fetal tissues as appropriate.
- Acute serum (taken soon after exposure or symptom appearance) and convalescent serum (2 weeks later) should be taken wherever possible. The two samples are important to rule out false positive tests due to cross reactivity with similar viruses such as dengue.
- Provide overseas travel details and clinical history including the onset day of any symptoms. Onset date is extremely important to ensure that the most appropriate test is performed. Details of any previous flavivirus vaccine (e.g. Japanese encephalitis, yellow fever) or previous flavivirus illness (e.g. West Nile virus, dengue) can be important for the pathologist in test interpretation.
- Testing asymptomatic males for Zika virus following travel can be considered if a pregnancy is planned. Serology 4 weeks after the last potential exposure is usually recommended in this situation.
A positive Zika result for a male in the context of a couple planning pregnancy will need discussion to balance the benefits of waiting 6 months to conceive with the limited evidence available and the costs of delaying pregnancy.
For further information, refer to Information for travellers about Zika virus testing
Testing for Zika virus infection should be considered in the following situations:
ALL SYMPTOMATIC INDIVIDUALS with EITHER
- A history of travel within the last 2 weeks to a Zika affected country or a country where there is the potential for Zika transmission OR
- A history of sexual exposure(vaginal/oral/anal) to a person diagnosed with Zika virus OR
- A history of sexual exposure(vaginal/oral/anal) to a person who has travelled to a Zika affected country or a country where there is the potential for Zika transmission
ASYMPTOMATIC PREGNANT WOMEN who
- Have travelled to a Zika virus affected country or a country where there is the potential for Zika transmission OR
- Have had sexual exposure to a traveller from a Zika affected country.
ASYMPTOMATIC MEN or WOMEN who
- Have travelled to a Zika affected country or a country where there is the potential for Zika transmission AND
- Are unable to wait the recommended duration for avoiding pregnancy or unprotected sex
Refer to Summary recommendations regarding Zika virus prevention for the relevant time periods.
Travellers to a Zika affected country or a country where there is the potential for Zika transmission should have an individual risk assessment to see if testing is indicated.
Testing is NOT advised for asymptomatic travellers where neither they nor their partner is pregnant or at risk of pregnancy.
For asymptomatic people, serological testing should occur at least 4 weeks after the last day in a Zika affected country. It may be advisable to also collect samples from an earlier date. False positive and false negatives can occur, however a negative result can be reassuring. A positive Zika result in the context of a couple planning pregnancy will need careful discussion to balance the benefits of waiting 6 months to conceive with the limited evidence available and the costs of delaying pregnancy.Testing for Zika virus can be difficult to interpret, please discuss with pathologist at the time of test request to ensure correct testing is requested and adequate information is given to the pathologist.
No specific antiviral treatment is available for Zika virus. Treatment is generally supportive and can include rest, fluids, and use of analgesics and antipyretics. Due to similar geographic distribution and symptoms, patients with suspected Zika virus infection also should be evaluated and managed for possible dengue or chikungunya virus infection. Aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) should be avoided until dengue can be ruled out to reduce the risk of haemorrhage.
There is a risk of transmission of Zika virus from infected returning travellers in areas of North Queensland where a suitable vector (Aedes aegypti) exists and is currently considered dengue receptive. In these areas, public health authorities follow up on notified cases to mitigate the risk of local transmission. Cases in areas where transmission could occur will be advised to take additional measures to avoid being bitten by mosquitoes.top of page
There is no vaccine for Zika virus. Prevention relies on avoiding being bitten by mosquitoes in countries where Zika virus occurs. Safe sex practices are also important in preventing sexual transmission.
Individual Risk assessment
All travellers are advised to undertake a pre-travel risk assessment with their doctor. This should include evaluation of the factors below:
- Whether the individual or their sexual partner is at increased risk of congenital complications of Zika virus infection because they are:
- not using reliable contraception;
- planning pregnancy;
- their partner is pregnant;
- their partner is at risk of pregnancy.
- Whether the individual may have potential exposures to Zika, including:
- the risk level of the country/countries travelling to or living in;
- the length of time in the country/countries;
- having unprotected sex;
- the likelihood of mosquito bites.
|Higher likelihood of mosquito bites||Lower likelihood of mosquito bites|
- The level of comfort the individual has with risk, perceived risk or uncertainty
- If the individual is returning to north Queensland and post travel mosquito precautions are required.
- The likelihood of sexual transmission of Zika following return
- Any other factors relevant to the individual
Relevant advice regarding Zika can then be tailored to the individual in addition to usual travel advice.top of page
Avoiding mosquito bites
All travellers are advised to take the following mosquito bite prevention measures when travelling to a Zika affected country or a country where there is potential for Zika transmission or wherever mosquito borne diseases are present. These precautions are necessary in the daytime as well as night time.
- Cover as much exposed skin as possible, including wearing light coloured long-sleeved shirts and long pants.
- Use insect repellents, per manufacturer’s instructions. 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 using 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).
- Stay and sleep in screened-in or air-conditioned rooms.
- Use bed nets as necessary.
Avoiding mosquito bites after return
On return from a Zika affected country people who live in or travel to areas of Australia where dengue outbreaks can occur should avoid mosquito-bites for 3 weeks following their return by strictly following mosquito bite prevention measures (refer to section “Mosquito bites” above). This is to help prevent spread from a traveller to the local mosquito population.
Preventing Sexual transmission
These recommendations are based on the evidence from published studies about the longest known time periods for persistence of Zika virus RNA in semen and in the female genital tract, and on the longest known time periods from onset to sexual transmission, refer to the section Transmission. The advice differs somewhat from the current advice of the World Health Organization,29 particularly with respect to periods of safe sex and pregnancy deferral for women, but the WHO has noted their recommendations are conservative and based on the lack of data on duration of persistence and infectivity.
To minimise the risk of sexual transmission to a pregnant woman:
Pregnant women should avoid unprotected sex with any partner who has been to a Zika area of risk for the duration of the pregnancy.
Women who are planning or at risk of pregnancy should be advised to avoid pregnancy during travel to a Zika area of risk and should avoid unprotected sex and pregnancy for at least 8 weeks following return. Advice relating to a partner who has travelled also applies.
For men with a partner who is planning pregnancy or at risk of pregnancy and who have travelled to a Zika area of risk or has a confirmed Zika infection (clinical or laboratory), pregnancy should be deferred for least 3 months after return, or 3 months after the date that Zika virus infection was diagnosed.
Anyone who is planning a pregnancy should be offered advice about the possibility of testing to help exclude Zika virus infection, particularly if there are concerns about the consequences of delaying pregnancy for the recommended time periods. Refer to Laboratory testing.
It should be noted that a range of communicable diseases pose particular risks for pregnant women (such as malaria) and Zika virus is only one consideration.
To minimise the risk of sexual transmission for all other men and women:
- If a female partner has travelled or been potentially exposed, avoid unprotected sex for at least 8 weeks after the last day in a Zika affected country or for 8 weeks after diagnosis.
- If a male partner has travelled or been potentially exposed, avoid unprotected sex for at least 3 months after the last day in a Zika affected country if no symptoms appear, or at least 6 months from time of diagnosis of infection.
A reliable method of contraception should be used to avoid pregnancy.
Advice to travellers returning from a country where there is a potential for Zika transmission should be based on an individual risk assessment.
Do not donate sperm for at least 6 months from the time of last exposure or time of diagnosis.
- For some couples where pregnancy is not a risk, and who do not reside in areas of Queensland where the vector is present, a longer or shorter period of abstinence from unprotected sex may be appropriate depending on an individual’s risk assessment and tolerance.
- Serological tests may be used to exclude infection in asymptomatic couples planning pregnancy.
- Unprotected sex refers to any form of sex that exposes the other person to genital secretions including vaginal, oral and anal. Barriers such as male or female condoms may be used to prevent Zika virus transmission.
Advice for residents of Zika area of risk who are planning a pregnancy
An individual risk assessment with a doctor should be undertaken as part of pregnancy planning for all women residing in a Zika affected country. This should include a discussion of the risks and an evaluation of the likelihood of contracting Zika for the woman and her partner. This will be based on information such as risk status of the area they reside in, travel, seasonal factors, accommodation type, activities undertaken, exposure to mosquitoes and other individual factors. The possibility of past Zika virus infection may also be relevant to a couple and testing may be available in some countries to help determine this.
A woman should defer pregnancy for at least 8 weeks following confirmed or clinical Zika virus infection.
If the male partner has had a confirmed Zika virus infection, defer pregnancy and unprotected sex for at least 3 months after diagnosis.
Refer to the CDC Clinical Guidance for Healthcare Providers for Prevention of Sexual Transmission of Zika Virus page for further details.
People who have been to a Zika affected country should not donate whole blood, clinical plasma or platelets for a minimum of 4 weeks after they have returned if they do not have symptoms of Zika virus infection.
If you are confirmed by a doctor to have Zika virus infection, you should not donate blood for 4 months after symptoms have ceased.
If you have had sex with someone who has been diagnosed with Zika virus infection at any time in the last 6 months, you should not donate whole blood for 4 weeks after the last time you had sex with that person.
For further information please refer to the Australian Red Cross Blood Service website.
A person who has been to a Zika affected country should defer donation of whole blood, clinical plasma or platelets for a minimum of 4 weeks after they have returned if they do not have symptoms of Zika virus infection.
A person diagnosed with Zika virus infection should be advised that they cannot donate blood for a minimum of 4 months after symptoms have ceased.
Sexual Contact Deferral
A sexual contact of a person diagnosed with Zika virus infection should be advised that they cannot donate blood for a minimum of 4 weeks after sexual contact (vaginal, oral, or anal) with someone who:
- Has current Zika virus infection; or
- Has recovered from Zika virus infection in the preceding 6 months.
Zika virus infection is notifiable in Australia as a flavivirus (unspecified) infection and should be notified to state and territory health departments. To guide reporting, the surveillance case definition is located on the Department of Health website.
In North Queensland and parts of Central and Southwest Queensland where mosquito vectors are present, clinicians should immediately report clinically suspected cases of Zika virus infection to local public health units, as they do for suspected cases of dengue.
People infected with Zika should be protected from further mosquito exposure during the first few days of illness to prevent other mosquitoes from becoming infected and reduce the risk of local transmission.
In Australia, this is relevant to confirmed cases in Queensland. Confirmed cases who are not residents in Queensland should be advised to avoid travel to these areas until their symptoms have resolved.
In parts of Queensland where the Aedes vector is known to be present, public health vector control teams may respond to reduce the risk of local transmission. Outside these areas in Queensland, notification is the required public health action.
People with Zika should follow recommendations to prevent sexual transmission (refer to Summary recommendations regarding Zika virus prevention)
- For an explanation of the country categorisation for Zika, a fact sheet for pregnant women and the general public, and interim guidelines for assessment of pregnant women, refer to the Department of Health webpage.
- For updated information on Zika areas of risk and countries with the potential for Zika transmission, refer to the CDC Zika Travel Information page.
- European Centre for Disease Prevention and Control – Zika virus infection.
- The United States CDC Zika pages.
- For the latest travel advice refer to the Smartraveller website.
- To notify clinically suspected Zika virus infection in Queensland, contact the local public health unit.
- should strictly follow mosquito bite prevention advice, avoid pregnancy and avoid unprotected sex (vaginal, oral and anal)
- The goals of this advice are to prevent a pregnant woman from becoming infected with Zika virus, and to prevent sexual transmission of Zika virus to any sexual partners.
- All people with symptoms consistent with a Zika virus infection should be tested as appropriate. Discussion with a pathologist is advised.
- Seek advice from a pathologist on sample type and timing if testing asymptomatic people is considered.
- Unless specified, partner refers to male or female partner
- *Advice for travellersto a country where there is the potential for Zika transmission is determined by individual risk assessment. Advice for travellers to a Zika a rea of risk may also be tailored based on the outcomes of an individual risk assessment. Follow advice relevant to risk.
Advice for travellers to Zika affected countries
|Traveller||Travel Advice||Pregnancy advice||Sexual transmission advice||Testing|
|Pregnant female*||Consider deferring travel. If travelling, follow Zika travel precautions.||Avoid unprotected sex while travelling. Avoid unprotected sex for the duration of pregnancy or for 6 months (whichever is longer) with a male partner who has travelled to a Zika affected country. Avoid unprotected sex for 8 weeks with a female partner who has travelled to a Zika affected country.||Testing should be offered to all pregnant women who have potentially been exposed to Zika virus, either through travel or sex.|
Female planning or at risk of pregnancy (of childbearing age and not using reliable contraception*)
|Consider deferring travel or defer pregnancy. If travelling, follow Zika travel precautions.||Avoid pregnancy while travelling. Avoid pregnancy for at least 8 weeks after the last day in a Zika affected country or for 8 weeks after diagnosis. Advice relating to a partner who has travelled also applies.||Avoid unprotected sex for at least 8 weeks after the last day in a Zika affected country or for 8 weeks after diagnosis. Advice relating to a partner who has travelled also applies.||Testing of asymptomatic females planning pregnancy can be considered at least 4 weeks after the last day in a Zika affected country.|
|Females not at risk of pregnancy||Follow Zika travel precautions.||To minimise the risk of sexual transmission, avoid unprotected sex for at least 8 weeks after the last day in a Zika affected country or for 8 weeks after diagnosis.||Test if symptoms develop|
|Male with a pregnant partner*||Follow Zika travel precautions.||Avoid unprotected sex for the duration of the pregnancy or for 6 months after the last day in a Zika affected country or 6 months after diagnosis, whichever is longer.||Testing of asymptomatic men can be considered at least 4 weeks after the last day in a Zika affected country.|
|Male with a partner planning or at risk of pregnancy*||Follow Zika travel precautions.||Avoid pregnancy for at least 6 months after the date of return from aZika affected country or 6 months from time of diagnosis of infection.||Avoid unprotected sex for at least 6 months after the last day in aZika affected country if no symptoms appear, or at least 6 months from time of diagnosis of infection.||Testing of asymptomatic men can be considered at least 4 weeks after the last day in a Zika affected country if pregnancy is planned.|
|Male with a partner not at risk of pregnancy||Follow Zika travel precautions.||To minimise the risk of sexual transmission, avoid unprotected sex for at least 6 months after the last day in a Zika affected country, or at least 6 months from time of diagnosis of infection.||Test if symptoms develop.|
|Sperm Donor||Follow Zika travel precautions.||Do not donate sperm for at least 6 months from the time of last exposure or from time of diagnosis.||Do not donate sperm for at least 6 months from the time of last exposure or time of diagnosis.||Testing could be considered at least 4 weeks after the last day in a Zika affected country if pregnancy is planned.|
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