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 virus affected country.
New risk categories for Zika virus affected countries (refer to Zika virus affected countries)
The risk assessment for Zika virus transmission in countries uses current and historical information from a range of sources to make an assessment of current transmission of Zika virus.
Risk categories are determined using available surveillance data (which can vary in quality), information on response measures in the affected country, outbreaks occurring in nearby countries and advice from major public health agencies or the World Health Organization.
Countries in this risk category have evidence of widespread transmission of Zika virus occurring in the country, increasing the chance that a resident or traveller will be exposed to Zika virus. These countries are usually countries where Zika virus has not been reported before, and Zika virus generally spreads quickly through the population.
Countries in this risk category have often reported small numbers of cases over an extended period of time. New cases may occasionally be reported. Countries may also be reporting small numbers of cases at the beginning of an outbreak. Some countries may progress to being high risk, while others may remain in moderate risk category or progress to low risk. We do not know the risk of getting Zika virus in these countries, but it is thought to be lower than in high risk countries. However the risk is not zero. Small numbers of cases means that Zika virus transmission is occurring, and is a potential risk for travellers.
Low risk countries are those in which Zika virus has been present in the past but there are no reported cases of Zika virus transmission within the last three months. Low levels of unreported Zika virus transmission in these countries is possible, so although the risk remains very low, it is not zero.
The mosquitoes that spread Zika virus do not usually live at elevations above 2000metres. 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.
top of pageRefer to the table Summary recommendations regarding Zika virus prevention
Because Zika virus infection in a pregnant woman may cause severe birth defects, deferral of travel to High Risk countries for these women is recommended. If the woman does decide to travel, discussion with a doctor about preventing Zika virus transmission from mosquitoes and sexual partners is advised.
For Moderate risk countries, a pregnant woman should consider deferring travel, based on her individual risk assessment. Recommendations for pregnant women planning to travel to Low risk countries should be based on an individual risk assessment.
Women planning a pregnancy should either defer travel as described above, or defer pregnancy.
All travellers are advised to undertake a pre-travel risk assessment with their doctor. This should include:
The likelihood of mosquito bites occurring is impacted by season, altitude, activities undertaken, type of accommodation, mosquito bite precautions taken and other individual factors.
The likelihood of sexual transmission of Zika virus should also be determined.
In addition to usual travel advice, information regarding preventing mosquito bites and avoiding unprotected sex while travelling should be given.
No vaccine is available for Zika virus.
Avoid pregnancy for at least 8 weeks following return from a High or Moderate Risk country. This includes women diagnosed with a Zika virus infection and asymptomatic women.
Pregnant women should avoid unprotected sex with a partner (male or female) who has been to a High or Moderate risk country for the duration of the pregnancy.
All males and females should avoid unprotected sex for at least 8 weeks following return from a High Risk country. For those returning from a Moderate Risk country, this advice also applies if prevention of sexual transmission is considered to be important, such as if pregnancy is planned.
If a male partner has a confirmed Zika virus infection (clinical or laboratory), avoid pregnancy and unprotected sex for at least 6 months from the time of diagnosis.
Advice to travellers returning from Low Risk countries should be based on an individual risk assessment.
Zika virus is a flavivirus, closely related to dengue. It is transmitted to humans primarily through the bite of certain infected Aedes species 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.
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.5
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,6, 7, 8, 9 but female-to-male and male-to-male transmission has also been reported.10, 11 From these cases, it is known that the sexual transmission can occur before, during, or after symptoms. It is not known if people with Zika virus infection who never develop symptoms can transmit it through sexual activity although there has been one case of likely sexual transmission from an asymptomatic male.12 Current recommendations are cautious, as evidence is still emerging.
Zika virus RNA has also been found in the semen of one (1) case up to 93 days following infection.13
top of pageApproximately one person in five who becomes infected with Zika virus is likely to have symptoms.14 For cases with a clinical illness, symptoms may include one or more of:
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. There is no specific therapy for Zika virus infection and 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. Reports from several countries, most notably Brazil, where Zika virus outbreaks have occurred indicate that there has been a coincident increase in cases of congenital abnormalities, some of which were severe, and include microcephaly.15, 16, 17, 18 Based on current evidence, the risk of congenital abnormalities appears to relate to all trimesters of pregnancy.19, 20, 21 Additional research is necessary and ongoing, to determine the likelihood and spectrum of adverse fetal outcomes associated with Zika virus infection.
Women are advised to undertake an individual risk assessment with their doctor. Those planning travel to High Risk countries are advised to defer travel and those travelling to Moderate Risk countries to consider deferring travel. Advice should be informed by the individual risk assessment.
Women should be advised to avoid pregnancy for at least 8 weeks following return from a High or Moderate Risk country. This includes women diagnosed with a Zika virus infection and asymptomatic women.
Pregnant women should avoid unprotected sex with a partner (male or female) who has been to a High or Moderate risk country for the duration of the pregnancy.
Advice to travellers returning from Low Risk countries should be based on an individual risk assessment.
For guidance on assessing pregnant women returning from Zika virus affected countries please refer to the Interim recommendations for assessment of pregnant women returning from Zika virus 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.
If the partner of a woman who is pregnant or planning pregnancy travels to a Zika virus affected country, please see the recommendations on sexual transmission.
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.
An individual risk assessment with a doctor should be undertaken as part of pregnancy planning for all women residing in a Zika virus affected country. This should include a discussion of the risks and an evaluation of the likelihood of contracting Zika virus in 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.
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 6 months after diagnosis.
Please refer to the CDC Interim guidance for health care providers caring for women of reproductive age with possible Zika virus exposure for further details.
top of pageSeveral countries that have experienced Zika virus outbreaks have reported increases in people who have GBS. Research suggests that GBS is associated with Zika virus, 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.
Please refer to the CDC website for further details.
Refer also to Summary recommendations regarding Zika virus prevention
No vaccine is available for Zika virus.
All travellers are advised to take the following mosquito bite prevention measures when travelling to a Zika virus affected country or wherever mosquito borne diseases are present. These precautions are necessary in the daytime as well as night time.
Medical advice should be sought as soon as practicable, if unwell with a high fever during or soon after travel.
On return from a Zika virus affected country, people who live in or travel to areas of Australia where dengue outbreaks can occur should avoid mosquito-bites for 4 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.
All Males and females should avoid unprotected sex for at least 8 weeks following return from a High Risk country. For those returning from a Moderate Risk country, this advice also applies if prevention of sexual transmission is considered to be important, such as if a pregnancy is planned.
If a male partner has a confirmed Zika virus infection (clinical or laboratory), avoid pregnancy and unprotected sex for at least 6 months from the time of diagnosis.
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.
Barrier protection should be used with all sexual partners, both male and female.
A person who has been to a Zika virus affected country should defer donation of blood for four (4) weeks after they have returned.
A person diagnosed with Zika virus infection should be advised that they cannot donate blood for a minimum of four (4) weeks after recovery of all symptoms.
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:
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 neutralizing antibodies.
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 infection may include IgM, IgG serology and PCR performed on blood, urine, amniotic fluid, cerebrospinal fluid or fetal tissues as appropriate.
For further information, please refer to Information for travellers about Zika virus testing
ALL SYMPTOMATIC INDIVIDUALS with EITHER
ASYMPTOMATIC PREGNANT WOMEN who
ASYMPTOMATIC MEN who
The recommended time periods are as follows:
With a pregnant partner – the duration of pregnancy
With a partner planning pregnancy – 8 weeks.
Testing is NOT advised for any other groups of asymptomatic travellers.
For asymptomatic people, testing should occur at least 4 weeks after the last day in a Zika virus affected country.
Testing for Zika virus can be difficult to interpret, please discuss with pathologist at the time of test request to ensure correct testing is ordered and adequate information is given to the pathologist.
top of pageNo specific antiviral treatment is available for Zika virus infection. 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 infections 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.
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 virus 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 infected Zika virus infection should follow recommendations to prevent sexual transmission (refer to Summary recommendations regarding Zika virus prevention)
Travel precautions for ALL TRAVELLERS to Zika virus affected countries
Notes:
| Traveller | Travel Advice | Pregnancy advice | Sexual transmission advice | Testing |
|---|---|---|---|---|
| Pregnant female | Defer travel to high risk countries. Consider deferring travel to Moderate risk countries. If travelling, follow Zika virus travel precautions. | Avoid unprotected sex while travelling in a Zika virus affected country. Avoid unprotected sex for the duration of pregnancy with a partner who has travelled to a ‘Zika virus affected’ country. | Testing should be offered to pregnant women who have potentially been exposed to Zika virus, either through travel or sex. | |
| Female currently attempting pregnancy | Defer travel to high risk countries or defer pregnancy. Consider deferring travel to moderate risk countries. If travelling, follow Zika virus travel precautions. | Avoid pregnancy while travelling in high or moderate risk countries. For confirmed infection OR potential exposure, wait at least 8 weeks following the last day in a ‘Zika virus affected’ country before attempting conception. Advice relating to a partner who has travelled also applies. | Avoid unprotected sex for at least 8 weeks after the last day in a high or moderate risk country. If a male partner has a confirmed Zika virus infection, avoid unprotected sex for 6 months from the time of diagnosis. |
Testing of couples planning pregnancy can be considered at least 4 weeks after the last day in a ‘Zika virus affected’ country. |
| Female at risk of pregnancy (of childbearing age and not using a reliable form of contraception) or planning pregnancy |
Follow Zika virus travel precautions. | Avoid pregnancy while travelling in high or moderate risk countries. For confirmed infection OR potential exposure, wait at least 8 weeks following the last day in a ‘Zika virus affected’ country before attempting conception. Advice relating to a partner who has travelled also applies. | Avoid unprotected sex for at least 8 weeks after the last day in a high or moderate risk country. If a male partner has a confirmed infection, avoid unprotected sex for 6 months from the time of diagnosis | Testing of couples planning pregnancy can be considered at least 4 weeks after the last day in a ‘Zika virus affected’ country. |
| Female NOT at risk of pregnancy OR Male or female with a partner NOT at risk of pregnancy |
Follow Zika virus travel precautions. | Avoid unprotected sex for at least 8 weeks after the last day in a high or moderate risk country. If a male partner has a confirmed Zika virus infection, avoid unprotected sex for 6 months from the time of diagnosis. |
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| Male or female with a pregnant partner | Follow Zika virus travel precautions. | Avoid unprotected sex for the duration of the pregnancy. | Testing of asymptomatic men can be considered at least 4 weeks after the last day in a ‘Zika virus affected’ country. | |
| Male with a partner at risk of pregnancy (of childbearing age and not using a reliable form of contraception) or planning pregnancy |
Follow Zika virus travel precautions. | Avoid pregnancy for at least 8 weeks after return from a high or moderate risk country. If a male traveller has a confirmed Zika virus infection, avoid pregnancy for 6 months from the time of diagnosis. |
Avoid unprotected sex for at least 8 weeks after the last day in a high or moderate risk country. If a male traveller has a confirmed Zika virus infection, avoid unprotected sex for 6 months from the time of diagnosis. |
Testing of asymptomatic men can be considered at least 4 weeks after the last day in a ‘Zika virus affected’ country. |
| Sperm Donor | Follow Zika virus travel precautions. | Do not donate sperm for at least a) 8 weeks if remain asymptomatic, or b) 6 months from the time of diagnosis if a Zika virus infection is confirmed |
Do not donate sperm for at least a) 8 weeks if remain asymptomatic, or b) 6 months from the time of diagnosis if a Zika virus infection is confirmed |
