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Risk assessment


​The full risk assessment [PDF] is available by clicking the link above. A summary of the conclusions is provided below.

Main conclusions and options for response

Event background

Given the current circulation of Zika virus; 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) and the risk of local vector-borne transmission in Europe during the 2016 summer season, EU/EEA Member States are recommended to consider a range of mitigation measures.

The following uncertainties have been taken into consideration when developing the proposed options for response:

  • There is growing evidence that Zika virus infection during the first and second trimester is associated with increased risk for CNS malformations and microcephaly. The risk of CNS malformations when the infection occurs during the third trimester is unknown, hence Zika virus infection should be considered as a risk throughout the entire duration of pregnancy.
  • Viable Zika virus have been detected in semen up to 24 days after onset of symptoms of Zika virus infection. The longest interval reported between the onset of symptoms in an infected man and the subsequent onset of disease in a female sexual partner is between 34 and 41 days.
  • The majority of the reported sexual transmission events are linked to symptomatic index cases. There is just one probable transmission from an asymptomatic sexual partner reported in the literature to date.

Information for travellers and EU citizens residing in areas with active local transmission 

A list of countries and territories with active transmission (i.e. sporadic and widespread transmission) during the past three months is available on the ECDC website.

  • Travellers visiting countries where there is active transmission of Zika virus and EU citizens residing in these countries should:
    − be made aware of the ongoing outbreak of Zika virus infection and the fact that Zika virus is usually transmitted by mosquitoes, but can be also transmitted by sexual intercourse.
    − take measures to prevent mosquito bites indoors and outdoors, especially between sunrise and sunset when Aedes mosquito vectors are most active. These measures include:
    • using mosquito repellent in accordance with the instructions indicated on the product label;
    • wearing long-sleeved shirts and long trousers, especially during the hours when the type of mosquito that is known to transmit the Zika virus (Aedes) is most active;
    • sleeping or resting in screened or air-conditioned rooms, otherwise using mosquito bed nets, at night and during the day.
  • Pregnant women and women who are planning to become pregnant and planning to travel to areas with widespread transmission should postpone non-essential travel.
  • Pregnant women and women who are planning to become pregnant and planning to travel to areas with sporadic transmission should consult their physician or a travel clinic and consider postponing non-essential travel.
  • Pregnant women residing in countries with active transmission (sporadic and widespread) should consult their healthcare providers for advice and follow strict measures to prevent mosquito bites.
  • Travellers with immune disorders or severe chronic illnesses should consult their doctor or seek advice from a travel clinic - particularly as regards effective prevention measures - before travelling to countries with active transmission.
  • Travellers to countries with active Zika transmission and EU citizens residing there should be advised that using condoms is likely to reduce the risk of sexual transmission.

Information for travellers returning from areas with local transmission of Zika virus.

  • Pregnant women who have travelled or resided in areas with active transmission should mention their travel during antenatal visits in order to be assessed and monitored appropriately.
  • In order to protect the foetus, male travellers returning from areas with active transmission should consider using a condom with a pregnant partner until the end of her pregnancy.
  • Travellers returning from areas with ongoing Zika virus transmission should be advised to use a condom for at least eight weeks after returning, in order to reduce the potential risk of onward sexual transmission. If before or during that period Zika virus symptoms occur, men should use condoms or consider abstinence for at least six months.
  • Travellers, including those with immune disorders or severe chronic illnesses, who develop symptoms compatible with Zika virus disease within two weeks of returning from an area with active transmission, should contact their healthcare provider and mention their recent travel.
  • All travellers, irrespective of symptoms, who return from an area with Zika virus transmission to an area in the EU/EEA where Aedes aegypti or Aedes albopictus mosquitoes are active, should take measures to prevent mosquito bites for three weeks so that they do not pass Zika virus to uninfected mosquitoes.with active transmission are
    advised to contact their healthcare provider and mention their recent travel.

Surveillance of imported cases and local transmission in the EU Member States of continental Europe

  • Increase awareness among clinicians and travel health clinics of the evolution of the Zika virus outbreak and the areas around the world with active and past transmission (ECDC website) to allow them to consider Zika virus infection in their differential diagnosis for travellers from those areas. Clinicians should be aware that Zika virus infections can be paucisymptomatic.
  • Enhance vigilance towards the early detection of imported cases of Zika virus infection into EU Member States, EU Overseas Countries and Territories (OCTs) and EU Outermost Regions (OMR), in particular where Zika vectors are present, in order to reduce the risk of onward autochthonous transmission.
  • Clusters of unexplained illness with a rash, detected in receptive areas of continental Europe between 1 May and 31 October should be investigated, and Zika virus infection should be considered as a possible cause.
  • Ensure timely reporting of autochthonous cases, in particular 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).
  • Increase 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 Guillain-Barré syndrome.

Information to healthcare providers in EU Member States

It is important to ensure that Zika virus-infected patients in areas with Aedes mosquito vectors avoid getting bitten during the first week of illness (e.g. bed nets, screened doors and windows as recommended by PAHO/WHO).

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. 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 clinicians assessing returning travellers, especially pregnant women, –who have visited countries and territories with recent or current local active transmission of Zika virus.

Due to the unprecedented size of the Zika virus epidemic, health services and practitioners should be alerted to the association between Zika virus infections and GBS, the possible association 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

Competent authorities, establishments and clinicians dealing with substances of human origin (SoHO) need to be vigilant about the risk of donor-derived Zika virus transmission through transfusion and transplantation. Measures should be taken to prevent Zika virus transmission through SoHO in both affected and non-affected areas. Implementation of safety measures related to SoHO should be informed by risk assessments performed at the national level. The European Commission’s Directorate General for health and food safety has established a working group for the preparation of a European preparedness plan for the safety of substances of human origin in the event of a Zika virus outbreak.

More in the ECDC risk assessment

See also the guide for SoHO safety preparedness activities at EU level.

Preparedness in the EU

Preparedness for the prevention and control of Zika virus infection in the EU/EEA will require capacities and capabilities for early detection, response and communication. ECDC has published a preparedness planning guide for diseases transmitted by Aedes aegypti and Aedes albopictus. The guide focuses on the main components that should be considered when developing preparedness plans.

More in the ECDC risk assessment



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