Zika virus and safety of substances of human origin : a guide for preparedness activities in Europe : first update

This first update of the original guide was prompted by the evolution of the Zika virus epidemic, a new classification of countries and areas based on their epidemiological profile, and recent scientific developments since the first edition of this guide. This summary contains only main changes that have been introduced into the update. Despite a dramatic global decrease in the incidence of Zika virus infections in 2017, there is still need to be vigilant and use risk reduction measures in EU Member States. Introduction and spread of the imported virus is possible during the mosquito season in all Member States that have permissive climate conditions and competent vectors. Data, though limited, indicate that there is a risk of Zika virus transmission through substances of human origin (SoHO), especially by blood transfusion. The high proportion of asymptomatic cases, documented occurrence of Zika RNA-positive blood donations and reports of probable transfusion-transmitted (TT) cases indicate that Zikapositive blood, donated by asymptomatic infectious donors, may enter the blood supply and henceforth could be transfused to a patient. However, the low number of TT cases, all without clinical consequences in recipients, preclude a more accurate risk assessment. Cases of donor-derived Zika-virus associated Guillain-Barré syndrome (GBS) have not been reported. Moreover, the likelihood of maternal and foetal exposure to blood products and presumably to other SoHO is very small. Data on Zika virus infection in donors of cells, tissues and organs and transmission of the virus to the transplant recipients are lacking. Nevertheless, the clear association between Zika virus infection and congenital malformations and GBS justifies the implementation of preventive measures to reduce the risk of transmission via the SoHO supply.