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The Communicable Disease Network Australia has updated recommendations to prevent sexual transmission of Zika virus. Information relating to Zika is available on the Department of Health website.
Note that the main transmission pathway for Zika is via mosquitoes. Please always recommend good mosquito precautions to patients travelling to countries where mosquito-borne illnesses are present.
Central, Southwest and North Queensland are the only places in Australia with the types of mosquitos that can transmit Zika virus. To protect others, travellers returning to this area from countries with current or recent local transmission of Zika (‘Zika-affected countries’) should ensure they practise good mosquito bite prevention for 4 weeks after return.
This information is provided to assist GPs in discussions with their patients about the risks of sexual transmission and pregnancy associated with travel to ‘Zika affected countries’.
Key points about Zika and the risk of sexual transmission
- As of 1st July 2016, there have been 60 cases of confirmed or probable Zika virus infection reported in Australia in 2016. There have been no recognised instances of sexual transmission in Australia and no cases of congenital infection.
- As of 29 June 2016, 10 countries had reported instances of sexual transmission of Zika virus. The USA has reported 13 sexually transmitted infections in 2016 out of a total of 935 travel-associated cases (1).
- Zika virus causes symptomatic illness in 20 % of those infected – up to 80% are asymptomatic.
- Zika virus infection in pregnant women can result in severe birth defects including microcephaly. The absolute risk is currently unknown. The fetus appears to be most vulnerable in the first trimester but the risk is thought to persist throughout pregnancy.
- Zika virus infection can cause Guillain-Barré syndrome but this is rare.
- The main transmission pathway is via mosquitoes, in particular the Aedes aegypti mosquito that, in Australia, is found in Central, Southwest and North Queensland. The Torres Strait has an additional vector, Aedes albopictus.
- To date, all documented sexual transmission of Zika virus has been reported to be from males with symptomatic infection to their partner usually with vaginal sex, apart from one documented case of transmission by oral sex, and one by anal sex in a male-to-male sexual contact. Zika virus has been detected in semen up to 62 days post infection (2).
- It is unknown if males with an asymptomatic infection can transmit Zika virus through sexual activity. There is one case reported where transmission of this kind possibly occurred (3).
- It is unknown if women can transmit Zika virus to men via sexual contact. This has not been documented.
The recommendations below are based on the known incubation period (estimated 3-12 days) and duration of illness (2-7 days) of Zika virus and longest known duration of Zika virus detection in semen (62 days). The recommendations have been updated to ensure consistency with guidance from the World Health Organization and the US Centers for Disease Control and Prevention and are cautious, noting that evidence is still emerging and the potential for variability in an individual’s immune system response.
- All travellers should protect themselves from mosquitoes to prevent Zika virus infection and other mosquito-borne infections
- All travellers should practise safe sex while travelling to ‘Zika-affected countries’
- If travellers develop symptomatic illness suggestive of Zika, testing should be performed
Recommendations for travellers to (or returning from) ‘Zika-affected countries’ regarding sexual transmission where there is pregnancy or risk of pregnancy
Aim: to reduce the risk of sexual transmission followed by vertical transmission to the fetus
Pregnant female traveller or female traveller currently attempting to become pregnant
Non pregnant female traveller at risk of pregnancy*/planning pregnancy
- Avoid unprotected sex AND avoid pregnancy while travelling in a “Zika-affected country”
- On return from a ‘Zika-affected country’, avoid pregnancy for at least 8 weeks from the last day in the country
- If the male partner also travelled to a ‘Zika-affected country’, pregnancy should be avoided for at least 8 weeks from the last day in country if the male is asymptomatic and at least 6 months from the time of diagnosis if he suffered symptomatic illness /confirmed Zika virus infection
*of childbearing age and not using effective contraception
Male traveller with a pregnant partner
- Avoid unprotected sex for the duration of pregnancy
Male traveller with a partner at risk of pregnancy* or planning pregnancy
- Male with confirmed Zika virus infection - avoid unprotected sex while travelling and for at least 6 months from time of diagnosis. Reliable contraception should be used by partners at risk of pregnancy for this time
- Male traveller with no Zika-compatible illness - avoid unprotected sex while travelling and for at least 8 weeks after return. Testing may be considered at least 4 weeks after the last day in a ‘Zika-affected country’ to exclude asymptomatic infection (refer below)
*of childbearing age and not using effective contraception
Recommendations for travellers to ‘Zika-affected countries’ regarding sexual transmission where there is no risk of pregnancy
Aim: to reduce sexual transmission of Zika virus
Female traveller with no risk of pregnancy
- Avoid unprotected sex while travelling
- If a male partner also travelled, follow the additional relevant advice below
Male traveller with partner* at no risk of pregnancy
- Avoid unprotected sex while travelling and for at least 8 weeks after return. If infection is confirmed, avoid unprotected sex for at least 6 months from time of diagnosis
*male or female
Discuss testing with your pathologist prior to ordering any tests.
For advice on testing for pregnant woman refer to the Department of Health website.
Where appropriate, in order to exclude Zika virus infection in an asymptomatic male traveller, serological testing at least 4 weeks after last potential exposure can be considered, particularly if a couple wish to conceive. Serology can be difficult to interpret due to cross reactivity with other flaviviruses. Discuss requests and results with a pathologist.
Information on testing
- Zika virus disease in the United States 2015-2015. CDC. [Online] [Cited: 17 06 2016.] https://www.cdc.gov/zika/geo/united-states.html.
- Detection of zika virus in semen (letter). Atkinson B, Hearn P, Afrough B, et al. 2016:22. Epub, February 11, 2016, Emerg Infect Dis.
- Sexual transmission of Zika virus in an entirely asymptomatic couple returning from a Zika epidemic area, France, April 2016. Freour T, Mirallie S, Hubert B, et al. 23, s.l.: Eurosurveillance, Vol. 2 . DOI: http://dx.doi.org/10.2807/1560-7917.ES.2016.21.23.30254.
Table of recommendations regarding Zika virus sexual transmission
Travel precautions for ALL TRAVELLERS to countries with current or recent local transmission of Zika (‘Zika-affected’)
- Strictly follow good mosquito precautions
- Avoid pregnancy
- Avoid unprotected sex (vaginal, oral and anal)