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Reducing the risk of Zika transmission

 

​ECDC regularly updates its risk assessment on the Zika virus epidemic. See below the latest update of the risk assessment [full PDF], an overview of all latest scientific findings considered in the update, as well as a summary of the conclusions and options for mitigation.

 

 ECDC RISK ASSESSMENT

 

Conclusions and options for response

European Union/European Economic Area (EU/EEA) Member States should consider a range of mitigation measures regarding the Zika virus epidemic due to:

  • the current circulation of Zika virus on several continents
  • the evidence of an association between Zika virus infection during pregnancy and congenital malformations of the central nervous system (CNS)
  • the association between Zika virus infection and Guillain–Barré syndrome (GBS)
  • the risk of local vector-borne transmission in Europe in areas where potential vectors are still active (e.g. Madeira) during the 2016 autumn season; in the continental EU, the risk of local vector-borne transmission will decrease in the coming months because the season for Zika virus transmission by vectors will become unfavourable
  • the possibility of sexual transmission from returning travellers
  • the risk of Zika virus transmission via substances of human origin (SoHO). The options for risk reduction and the definitions below are based on the current evidence, which take into account current uncertainties. These are subject to change as new evidence emerges.

Options for risk reduction

The predominant mode of transmission of Zika virus is through the bites of infected mosquitoes but the virus can also be transmitted through sexual contact, and by blood and blood components and possibly by other substances of human origin. Pregnant women are the most important risk group and the primary target for preventive measures because Zika virus infection during pregnancy is associated with intrauterine CNS infection, congenital malformations and foetal death. A map and list of countries and territories with widespread and sporadic transmission during the past three months is available on ECDC website.

Preventive measures   

 

Preventing mosquito transmission  

Mosquito-borne transmission occurs when an infective mosquito bites a susceptible person. The risk of mosquito-borne transmission can be reduced by lowering the mosquito population density and by applying personal protective measures against being bitten. The aim is to prevent susceptible people from being bitten by infective mosquitoes, and preventing infected people from being bitten by competent mosquitoes to prevent the continuation of the chain of transmission.

Personal protective measures that reduce the risk of mosquito bites and which should be applied indoors and outdoors are:

  • use of mosquito repellent in accordance with the instructions indicated on the product label
  • wearing long-sleeved shirts and long trousers, especially during the daytime, when the Aedes aegypti and Aedes albopictus mosquitoes are most active
  • sleeping and resting in screened or air-conditioned rooms, or using mosquito bed nets at night and during the day. 

Preventing sexual transmission  

Zika virus sexual transmission can be prevented by:

  • abstaining from sexual contact with a potentially infectious person; OR
  • consistent use of barrier methods* during sexual contact with a potentially infectious person**.

Advice to populations at risk

Residents in affected areas***

  • All residents in affected areas are at risk of Zika virus infection unless they have immunity due to a previous infection. Residents should consider taking measures to prevent mosquito-borne and sexual transmission of the virus.
  • Pregnant women residing in affected areas should consult their healthcare providers for medical advice. They should strictly follow measures to prevent mosquito and sexual transmission for the duration of their pregnancy. Pregnant women should seek medical attention if they develop symptoms compatible with Zika virus infection.
  • Women of childbearing age should be made aware of the risks of Zika virus infection to the foetus during pregnancy and the possibility of sexual transmission through unprotected sex with a potentially infectious person.
  • Women and men living in affected areas should discuss pregnancy planning with their healthcare provider.

 

Travellers to affected areas

  • All travellers to affected areas are at risk of Zika virus infection unless they have immunity due to a previous infection. Travellers to affected areas should take measures to prevent mosquito-borne and sexual transmission of the virus. This is particularly important for the partners of pregnant women.
  • Pregnant women should seek medical advice prior to travelling. They should postpone non-essential travel to affected areas with widespread transmission and consider postponing non-essential travel to areas with sporadic transmission for the duration of their pregnancy.
  • Women of childbearing age who travel to affected areas should be made aware of the risks of Zika virus infection to the foetus during pregnancy and the possibility of sexual transmission. Therefore, they should take measures to prevent mosquito bites and follow recommendations for prevention of sexual transmission while in affected areas.
  • Travellers with immune disorders or severe chronic illnesses should consult their physician or seek advice from a travel clinic before travelling.

Persons returning from affected areas

  • All persons returning from affected areas should seek medical attention if they develop symptoms compatible with Zika virus infection within two weeks of arriving from the affected areas, and mention their travel history.
  • Pregnant women returning from affected areas should:
    • inform their antenatal care provider about their travel to an affected area
    • take measures to prevent sexual transmission for the duration of the pregnancy in order to minimise the risk of foetal exposure to Zika infection
  • Partners of pregnant women returning from affected areas should:
    • follow measures for prevention of sexual transmission for the duration of pregnancy in order to minimise the risk of foetal exposure to Zika virus infection.
  • Couples who want to conceive should consider the following options to minimise the risk of Zika congenital syndrome if one or both partners have been exposed (i.e. returning from an affected area or having had unprotected sexual contact with a potentially infectious partner):
    • Delay pregnancy for at least eight weeks after symptom onset or last possible Zika virus exposure for women, symptomatic or not
    • Delay conception for a duration of at least six months after symptoms onset or last possible Zika virus exposure for men, symptomatic or not
    • Discuss with their healthcare provider the period for deferring conception/pregnancy in relation to individual exposure characteristics and availability of test results.
  • All couples who are concerned about sexual transmission of Zika virus infection to their partner may consider the following option:
    • Take measures to prevent sexual transmission for at least eight weeks if the returning partner is a woman and six months if a man.
  • In addition, all persons who have been in affected areas and travel to areas where the vector is present and active should:
    • Take personal protective measures to prevent mosquito bites as described above, for three weeks after having left an affected area to prevent onward vector-borne transmission.  

Information to healthcare providers in EU Member States

  • Efforts should be made to increase awareness among health professionals providing antenatal care of the risk of neurological congenital syndrome associated with maternal Zika virus infection, especially during the first two trimesters of pregnancy. Pregnant women with exposure to Zika virus (including sexual exposure) since the beginning of their pregnancy should be investigated as part of the routine obstetric monitoring (Algorithm for public health management of cases under investigation for Zika virus infection).
  • Antenatal monitoring should be adapted in accordance with the possibility of exposure to the virus through vector or sexual transmission [1,2]. ECDC maps showing Zika transmission in the past nine months are provided to aid medical practitioners assessing returning travellers, especially pregnant women, who have visited countries and territories with recent transmission of Zika virus.
  • Health services and practitioners should be aware of the association between Zika virus infections and GBS, the possible associations with other neurological conditions (such as meningitis, meningoencephalitis and myelitis), and with as yet undocumented complications of Zika virus infections, particularly among children, the elderly, immunocompromised individuals and those with sickle cell disease.

Safety of substances of human origin 
 

There is no change in the level of risk of Zika virus transmission through SoHO compared to the previous Rapid Risk Assessment. The measures and main recommendations provided in the ECDC document ‘Zika virus and safety of substances of human origin – Guide for preparedness activities in Europe’ remain valid [3].

The European Medicines Agency (EMA) and competent authorities in the EU Member States have confirmed that there is no increased risk of Zika virus infection for recipients of plasma-derived or urine-derived medicines [4]. EMA’s Committee for Medicinal Products for Human Use Biologics Working Party (CHMP’s BWP) assessed that manufacturing processes for these products successfully inactivate or remove virus. Thus, additional safety measures such as the screening of plasma and urine donors or donations or the deferral of donors returning from affected areas are not considered necessary.

Surveillance of imported cases and local transmission in Europe


In order to reduce the risk of local transmission in Europe, EU Member States should:

  • Ensure that medical practitioners and travel health clinics are aware of the evolution of the Zika virus outbreak and the areas around the world with active and past transmission (see ECDC website) to allow them to consider Zika virus infection in their differential diagnosis for travellers coming from those areas, or for symptomatic individuals who have not travelled but had sexual activity with a returning traveller from those areas. Medical practitioners should be aware that Zika virus infections can be paucisymptomatic.
  • Maintain awareness among obstetricians, paediatricians and neurologists that the possibility of Zika virus infection should be investigated in patients presenting with congenital CNS malformations, microcephaly and GBS.
  • Remain vigilant towards the early detection of imported cases of Zika virus infection in EU Member States, EU Overseas Countries and Territories (OCTs) and EU Outermost Regions (OMR), particularly where Zika vectors are present and still active and which have not experienced local vector-borne transmission (e.g. Madeira), in order to reduce the risk of onward autochthonous transmission.
  • Ensure timely reporting of autochthonous cases, particularly in the receptive areas of EU Member States in continental Europe.
  • Strengthen laboratory capacity and capabilities to confirm Zika virus infections in the EU/EEA and to differentiate Zika virus infections from other arboviral infections (e.g. dengue, chikungunya). 

Notes:

* Barrier methods include: male or female condoms for penetrative sex, including sex toys, and male or female condoms or dental dams for oral–genital or oral–anal sexual contact. To increase their effectiveness they should be used consistently and correctly, for the entire duration of sexual contact (United Nations position statement on condoms and the prevention of HIV, other sexually transmitted infections and unintended pregnancy, 7 July 2015).
** A potentially infectious person is defined as: any person who resides in an affected area; OR a woman who has been in an affected area in the past eight weeks; OR a man who has been in an affected area in the past six months; OR a woman who has had unprotected sex in the past eight weeks with a potentially infectious person as defined above; OR a man who has had unprotected sex in the past six months with a potentially infectious person as defined above.
***Affected areas are areas where locally vector-borne transmitted cases of Zika virus infection have been reported in the past three months. ECDC classifies Zika-affected areas as having widespread transmission or sporadic transmission based on cases reported in the past three months.

References: 

1. Petersen EE, Polen KND, Meaney-Delman D, Ellington SR, Oduyebo T, Cohn A, et al. Update: Interim guidelines for health care providers caring for pregnant women and women of reproductive age with possible Zika virus exposure — United States, 2016. MMWR Morb Mortal Wkly Rep. 2016;65(12):315-22.
2. Olson CK, Iwamoto M, Perkins KM, Polen KND, Hageman J, Meaney-Delman D, et al. Preventing transmission of Zika virus in labor and delivery settings through implementation of standard precautions — United States, 2016. MMWR Morb Mortal Wkly Rep. 2016;65(11):290-2.
3. European Centre for Disease Prevention and Control. Zika virus and safety of substances of human origin. A guide for preparedness activities in Europe. 2016
4. European Medicines Agency. Zika virus infection: plasma- and urine-derived medicines safe to use [Press release]. 2016 Sep 21.
 

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