What is the issue?
Due to the rapid spread of Zika virus around the world and concerns about a temporal and geographical association between an observed increase in congenital microcephaly and outbreaks of Zika virus infection, the World Health Organisation declared a Public Health Emergency of International Concern on 1 February 2016.
Who is at risk?
Anyone travelling to a country where there is active Zika virus transmission is at risk of Zika virus infection.
Until more is known, the Department recommends people planning travel to countries with active Zika transmission, or returning from those countrues, take certain precautions:
- Pregnant women in any trimester and women who are trying to get pregnant should consider postponing travel to countries with active Zika virus transmission.
- All travellers should take steps to avoid mosquito bites whilst travelling in affected countries.
- People experiencing an illness compatible with Zika virus infection with symptom onset within two weeks of travel to a country with active Zika virus transmission, should seek medical advice and be considered for testing for Zika virus in addition to other causes of fever in a returned traveller, such as malaria and dengue.
- Pregnant women who are well and have returned from a country with active Zika virus transmission should seek medical advice and be considered for testing for Zika virus exposure.
There is strengthening evidence of an association between Zika infection and the occurrence of foetal malformations including microcephaly. There is also emerging evidence of an increase in neurological disorders after Zika virus infection, such as Guillain-Barre Syndrome.
The Australian Government is maintaining an up to date list of countries with epidemiological evidence of active Zika virus transmission within the past two months, based on nationally agreed criteria.
Symptoms and transmission
Zika virus is spread through the bite of mosquitoes of the genus Aedes, especially Ae. aegypti and potentially Ae. albopictus (the Asian tiger mosquito). Ae. aegypti is found in central and northern Queensland but is not known to be found in other parts of Australia. At this stage, there has been no local transmission of Zika virus in Australia, nor evidence of Zika virus in mosquitoes in Australia.
Zika virus infection is often asymptomatic. Only around 1 in 5 people infected with Zika virus will develop symptoms. When symptoms do develop, it takes 3-12 days after exposure, they are usually mild, and last for several days up to a week. For those who display symptoms, two or more of the following is consistent with clinical Zika virus infection: acute onset of fever, maculopapular rash, arthralgia or conjunctivitis with symptom onset within two weeks of travel to a country with active Zika virus transmission.
Zika virus is primarily transmitted through mosquito bites. There is increasing evidence that transmission can occur from mother to baby during pregnancy and through sexual intercourse. Zika virus has been found in the semen of men with symptomatic Zika virus infection; however the duration of persistence in the semen is currently unknown.
Men who have travelled to areas with ongoing Zika virus transmission should take the following precautions:
- Men who have travelled to areas with ongoing Zika virus transmission whose partner is pregnant should abstain from sexual activity (vaginal, anal, or oral) or consistently use condoms for the duration of the pregnancy, whether symptomatic or asymptomatic.
- Men who have had a confirmed Zika virus infection, whose partner is not pregnant should abstain from sexual activity (vaginal, anal, or oral) or consistently use condoms for 3 months following the resolution of symptoms.
Further information can be found at the Australian Government Department of Health website.
Generally, testing should be considered in people with symptoms of Zika virus infection and pregnant women with a history of recent travel to a country with active Zika virus transmission.
Travellers to areas with active Zika transmission are also generally at risk for malaria, dengue and chikungunya infection. When testing for Zika virus in a returned traveller from a country with active Zika virus transmission, medical practitioners should consider other causes of febrile illness including malaria. All testing for Zika virus in Victoria will be carried out through the Victorian Infectious Diseases Laboratory (VIDRL).
Laboratory specimens must be accompanied with a date of onset of symptoms and include country of exposure, dates of travel, symptoms, and pregnancy status.
Zika-specific PCR will generally detect Zika virus if blood is taken within five days of onset of illness, and in urine if taken within 14 days of onset of illness. Zika IgM probably rises from day 4 to 7 after onset of illness to last for up to 12 weeks, and Zika IgG probably rises from day 12 after onset of illness. Zika serology can be falsely positive due to cross-reactivity in a number of circumstances, including previous flavivirus infection (e.g. dengue) or flavivirus vaccination (e.g. yellow fever or Japanese encephalitis), and has to be interpreted with caution and in conjunction with infectious diseases specialist advice.
Interim recommendations for the assessment of pregnant women returning from Zika virus-affected areas have been developed by the Australian Department of Health. In all cases involving pregnant women, advice and counselling are important to enable the patient to make informed decisions regarding testing.
A person confirmed to have Zika virus infection should be advised not to travel to north Queensland for at least seven days after symptom onset, due to a risk of introducing Zika virus into local mosquito populations there.
When to notify the Department
Zika virus infection is a Group B notifiable condition under the Public Health and Wellbeing Regulations 2009 under "arbovirus infection – other" and must be notified in writing within 5 days of diagnosis. More information is available in the infectious diseases section.
In light of the rapidly evolving international outbreak, medical practitioners and laboratory services are requested to call the Department on 1300 651 160 on the same day in the following circumstances:
- Where a pregnant woman is being tested for Zika virus infection and there is a compatible clinical illness with onset within 14 days of travel to a country with active Zika virus transmission;
- Where a foetus or newborn child is diagnosed with microcephaly and the pregnant woman or mother has travelled to a country with active Zika virus transmission during the pregnancy;
- Where a patient has been diagnosed with Guillain-Barre syndrome after travel to a country with active Zika virus transmission.
No specific antiviral treatment is available for Zika virus infection. Treatment is supportive and can include rest, fluids, and use of analgesics and antipyretics. Because of similar geographic distribution and symptoms, patients with suspected Zika virus infections should also be evaluated and managed for possible malaria, dengue virus 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.
Information for obstetricians providing specialist care to pregnant women with confirmed Zika virus infection is available on the United States Centers for Disease Control website.
Information from the Royal Australian and New Zealand College of Obstetricians and Gynaecologists is available on the RANZCOG website.
Information for clinicians from the Australian Government Department of Health
Information from the United States Centers for Disease Control
Information on Zika virus infection at the Victorian Better Health Channel
Information on measures to avoid mosquito bites at the Victorian Better Health Channel
Travel advice from the Australian Government Smartraveller website
List of countries with current or recent local transmission of Zika virus from the Australian Government Department of Health
Remember, anyone returning from overseas who is concerned about their health should see a medical practitioner for advice.