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Updated rapid risk assessment on Zika virus in the Americas and potential complications

22 Jan 2016

​The Zika virus epidemic continues to spread in the Americas. Since the last ECDC rapid risk assessment published on 10 December 2015, 13 additional countries or territories have reported laboratory confirmed autochthonous transmission. Further information is now available on the number of babies born with microcephaly in Brazil and several Zika-affected countries have reported unusual increases in Guillain–Barré syndrome. ECDC has updated its assessment and options for mitigation in its new rapid risk assessment.

The risk assessment concludes that despite growing evidence of a link between intra-uterine Zika virus infection and adverse pregnancy outcomes, a causal link between these events has not yet been confirmed.  It also concludes that further epidemiological studies are required to assess the strength of the association between Guillain–Barré syndrome and Zika virus infection. No new scientific evidence about the association of Guillain-Barré and Zika virus infection has been published.

As of 19 January 2016, autochthonous cases of Zika virus infection were reported from 23 countries or territories worldwide within the past two months and 27 countries or territories have reported autochthonous cases within the past nine months.

The findings from investigations of an additional four suspected cases of microcephaly with a possible association to Zika virus infection were reported by the Brazilian authorities. In addition, a recent journal publication mentions six additional cases but with no further details. The Hawaii (USA) Department of Health announced a laboratory confirmed case of Zika virus infection in a baby born with microcephaly from a mother who was pregnant when she resided in Brazil in May 2015.

Two new countries, El Salvador and Venezuela, have reported an unusual increase above the baseline of Guillain-Barré syndrome, concomitant with the development of Zika outbreaks in the country. This observation supports a temporal and spatial association as that seen in French Polynesia.

Options for mitigation

The main options for mitigation that public health authorities in EU/EEA Member States should consider include the following (see the rapid risk assessment for the full description of the options):  
  • Increase awareness of clinicians and travel health clinics so Zika virus infection is considered in their differential diagnosis.
  • Enhance vigilance towards the early detection of imported cases.
  • Strengthen laboratory capacity.
  • Increase awareness among obstetricians, paediatricians and neurologists that Zika virus infections should be investigated for patients presenting with congenital central nervous system malformations, microcephaly and Guillain–Barré syndrome.


Safety of substances of human origin
  • Blood safety authorities should consider the deferral of donors with a relevant travel history to affected areas, in line with measures defined for dengue virus.


Information to travellers and EU residents in affected areas
Recent trends can be used to describe the affected countries as either:
  • Experiencing a rapidly evolving Zika virus epidemic with an increasing or widespread transmission; or
  • Reporting sporadic transmission following recent introduction.
The following options should be considered by public health authorities:
  • Advise all travellers to affected areas to take protective measures to prevent mosquito bites, including during the day.
  • Advise travellers with immune disorders or severe chronic illnesses to seek medical advice before travelling.
  • Advise pregnant women and women who are trying to become pregnant, to discuss travel plans with their healthcare providers and to consider postponing their travel to affected areas, especially to areas with increasing or widespread transmission.
  • Advise EU citizens who live in affected areas to take protective measures to prevent mosquito bites, particularly pregnant women and women who are trying to become pregnant living in areas with increasing or widespread transmission.
  • Travellers showing symptoms compatible with dengue, chikungunya or Zika virus disease within three weeks after returning from an affected area should contact their healthcare provider.
  • Pregnant women who have travelled to areas with Zika virus transmission should mention their travel during antenatal visits in order to be assessed and monitored appropriately.


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