Rapid risk assessment: Zika virus disease epidemic, eighth update

Risk assessment

This eighth update assesses the risks associated with the Zika virus epidemic currently affecting countries in the Americas. It provides updated information for those travelling to and returning from affected countries and for EU citizens residing in areas with active transmission. It reviews available information on the association between Zika virus infection and congenital central nervous system malformations, including microcephaly, as well as the association between Zika virus infection and Guillain–Barré syndrome. It also proposes a range of mitigation measures for EU/EEA Member States to consider.

Executive summary

In light of the latest scientific and epidemiological developments, ECDC has updated its rapid risk assessment on the Zika virus disease epidemic.

The outbreak is unprecedented in terms of size and public health impact. The evolution of the Zika epidemic in the Americas and other world regions demands close monitoring as it has a direct impact on the risk of importation and possible local transmission in the European Union. The viral circulation in affected countries coincides with the summer holiday period in Europe and it is expected that Zika viraemic travellers will continue to return to the EU during the entire 2016 European mosquito season. This will create the possibility of onward mosquito-borne transmission of Zika virus in receptive areas in Europe, however, no such cases have been reported to date.

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 foetal central nervous system congenital malformations.

The rapid risk assessment includes a revised presentation of the options for risk reduction and definition of terms in order to provide greater clarity for the range of different population groups. There have been no substantive changes to the options which cover:

  • Preventing mosquito-borne and sexual transmission
  • Advice to populations at risk and persons returning from affected areas
  • Information to healthcare providers in EU Member States
  • Safety of substances of human origin
  • Surveillance of imported cases and local transmission in continental Europe.

Since the last update to the rapid risk assessment of 8 July 2016, the outbreak has continued to evolve in Central America and the Caribbean and, notably, local mosquito-borne transmission has reached Florida, USA. Between 30 June and 17 August 2016, seven new countries and territories reported locally-acquired cases (Antigua and Barbuda, Bahamas, Cayman Islands, Turks and Caicos, United States of America, Guinea-Bissau and Federated States of Micronesia) and one new country reported non vector-borne Zika virus transmission (Spain). During the same period, three new countries (Honduras, Paraguay and Suriname) reported their first cases of microcephaly or central nervous system malformation associated with Zika virus infection and four new countries (Jamaica, Costa Rica, Grenada and Guatemala) notified cases of  Guillain-Barré Syndrome associated with Zika virus infection.