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Reducing the risk of Zika transmission

 

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

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
  • 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 during the 2016 summer season.

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. Pregnant women are the most important risk group and the primary target for preventive measures, as 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 the ECDC website.

Zika-affected areas

ECDC classifies Zika-affected areas as having widespread transmission or sporadic transmission based on cases reported in the past three months:

  • Widespread transmission: more than 10 locally transmitted cases of Zika virus in one area, OR local transmission of Zika virus in two or more areas, OR Zika virus transmission ongoing for more than three months.
  • Sporadic transmission: no more than 10 locally transmitted cases reported in a single area in the past three months.

For more information about the classification of Zika affected areas, please visit the ECDC website.

Zika unaffected areas

Unaffected areas are areas without mosquito-borne transmission of Zika virus. The unaffected areas in the EU/EEA are classified according to their potential for mosquito-borne transmission as:

  •  Receptive areas for Zika virus transmission: areas with established and active populations of Aedes aegypti or Aedes albopictus mosquitoes.
  •  Unreceptive areas for Zika virus transmission: areas with no established or inactive populations of Aedes aegypti or Aedes albopictus mosquitoes.

Potentially infectious person

A potentially infectious person is defined as:

  • a person who resides in an affected area; OR
  • a person 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 AND experienced symptoms while in the affected area or within two weeks after leaving the area; OR
  • a person, regardless of gender, who has had unprotected sex* in the past eight weeks with a potentially infectious person as defined in the three bullet points above.

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 and thus continue 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 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 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 infection.

Women of childbearing age should be made aware of the risks of Zika 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 planned pregnancy with their healthcare provider and consider delaying pregnancy.

Travellers to affected areas
All travellers to affected areas are at risk of Zika 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.

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 child-bearing age who travel to affected areas should be made aware of the risks of Zika infection to the foetus during pregnancy and the possibility of sexual transmission. Women of child-bearing age who travel to affected areas should be made aware of the risks of Zika infection to the foetus during pregnancy and the possibility of sexual transmission. Therefore, they should take measures to delay pregnancy until eight weeks after returning from the affected area. If their male partner has been exposed and had symptoms of Zika virus disease, conception should be delayed for six months after onset of symptoms.

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:

  • take measures to prevent sexual transmission for at least eight weeks after returning if asymptomatic, and six months for men who experienced symptoms while in the affected area or within two weeks after leaving the area
  • seek medical attention if they develop symptoms compatible with Zika 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 their pregnancy.

All persons who have been in affected areas and travel to receptive areas should:

 take personal protective measures to prevent mosquito bites as described above, for three weeks after having left an affected area.

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. 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

ECDC published a report on ‘Zika virus and safety of substances of human origin – Guide for preparedness activities in the Europe’ [4]. The objective of this document is to support the operational preparation and implementation of national preparedness plans for the safety of substances of human origin (SoHO) during outbreaks of Zika virus infection. This document includes detailed measures to be considered to mitigate the threats to the safety of SoHO posed by Zika virus. Non-affected areas and areas with sporadic transmission Blood donors and living donors of cells and tissues who are at risk of having been infected should be temporarily deferred from donation.

Criteria for identifying donors at risk are:

  •  a medical diagnosis of Zika virus disease
  •  returning from areas with widespread transmission
  •  reporting sexual intercourse with a person who has been diagnosed with Zika virus infection or a person who has returned from areas with widespread transmission.

The deferral/acceptance periods for living donors should provide a sufficient safety margin for virus-free donation. Cells and tissues from deceased donors with a recent medical diagnosis of Zika virus infection should not be accepted for donation.

Areas with widespread transmission

Temporarily interrupt donations and import blood components or cells and tissues from unaffected parts of the country, or continue with the selective donation of plasma, platelets and some tissues that should be pathogen inactivated, and import other products that cannot be inactivated. The laboratory screening of all donated blood and all donors of cells and tissues for the presence of Zika virus RNA by nucleic acid testing (NAT) may be considered necessary to ensure the safety and sustainability of supply in areas with widespread transmission.

Irrespective of the presence of ongoing local virus transmission in the area, the risk of Zika virus transmission through organs donated by living or deceased donors should be recognised and assessed during a pre-donation evaluation and balanced against the benefits of the transplantation for each potential recipient.

Laboratory screening of SoHO donors/donations

Commercial Zika tests for screening are still under development. SoHO establishments and laboratories may develop in-house or adapt available commercial diagnostic tests for screening purposes. The use of such screening tests should be validated and approved by the responsible national authority. WHO reference material of Zika virus RNA for comparative evaluation of both diagnostic and screening assays is expected to be officially endorsed in October 2016 but can already be obtained from the Paul-Ehrlich-Institute (Germany).

The commercial laboratory tests that are reviewed favourably in the WHO Emergency Use Assessment and Listing (EUAL) and listed as eligible for WHO procurement could also be used for an emergency application until final registration/approval for commercial use is available.

The recent non-binding recommendation by the US Food and Drug Administration (FDA) for the universal testing of donated whole blood and blood components for Zika virus in the USA and its territories will be reviewed in the European context.

Surveillance of imported cases and local transmission in continental Europe

In order to reduce the risk of local transmission in continental 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 pauci-symptomatic.
  • 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 GBS.
  • Enhance vigilance 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), in particular where Zika vectors are present, in order to reduce the risk of onward autochthonous transmission.
  • Ensure timely reporting of autochthonous cases, in particular in the receptive areas of EU Member States in continental Europe.
  • 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.
  • 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).
 

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