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

technical guidance
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 European Centre for Disease Prevention and Control. Zika virus and safety of substances of human origin: a guide for preparedness activities in Europe – first update. Stockholm: ECDC; 2017.

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In 2016, ECDC and multi-country working group developed a guide for preparedness activities in Europe with the objective 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 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. 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.

Since the issuing of the original guide, a revised scheme has been developed by WHO, in collaboration with the US CDC and ECDC, to categorise the epidemiological profile of vector-borne Zika virus transmission in countries and territories. The updated guide explains the measures for donor referral aligned with the new classification of countries and areas, and the measures for deferral of SoHO donors related to the latest findings on sexual transmission of Zika virus.

Executive summary

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. 

A revised scheme has been developed by WHO, in collaboration with the US CDC and ECDC, to categorise the epidemiological profile of vector-borne Zika virus transmission in countries and territories: Category 1 (area with new introduction or re-introduction with ongoing transmission); Category 2 (area either with evidence of virus circulation before 2015 or area with ongoing transmission that is no longer in the new or re-introduction phase, but where there is no evidence of interruption); Category 3 (area with interrupted transmission and with potential for future transmission); Category 4 (area with established competent vector but no known documented past or current transmission). A map depicting these categories of countries and areas is regularly updated by ECDC and may be used for applying SoHO safety measures1. In the C1 and C2 areas, the Zika virus transmission is active, while in the C3 and C4 areas, active transmission of Zika virus is absent. The working group behind this guide agreed that only areas with active transmission of Zika virus are relevant for the implementation of SoHO safety measures. Thus, for the purpose of this guide, C1 and C2 areas are considered as ‘areas with active transmission’ while in C3 and C4 areas, and areas not at risk of ongoing vector-borne transmission, are considered as ‘areas without active transmission’. 

In the areas without active transmission, a temporary deferral from the donation of blood and/or non-reproductive cells and tissues for 28 days is suggested after cessation of disease symptoms, return from an area with active transmission and sexual contact with a Zika-infectious person. In order to harmonise this guide with the CDC’s and ECDC’s advice for sexual precaution against Zika virus transmission and to avoid unnecessary donor loss in areas without active transmission risk, a temporary deferral from donation of blood and/or non-reproductive cells and tissues for 28 days is suggested for donors after sexual contact with a man diagnosed with Zika virus infection in the six months preceding the sexual contact, or with a woman diagnosed with Zika virus infection in the eight weeks preceding the sexual contact.  In the areas without active transmission, a temporary deferral from sperm donation for six months is also recommended for donors after cessation of disease symptoms, return from an area with active transmission, or sexual contact with a man diagnosed with Zika virus infection in the six months preceding the sexual contact, or with a woman diagnosed with Zika virus infection in the eight weeks preceding the sexual contact.

The deferral periods due to the sexual exposure are applied as a precautionary measure because the duration of infectivity in sperm and vaginal fluid is currently unknown. Suggested periods will be revised if new evidence becomes available. The risk of Zika virus-positive blood donation after sexual contact with travellers returning from areas with active transmission has been estimated to be extremely low. Implementation of these measures, including a temporary deferral after sexual exposure to diagnosed persons or travellers returning from area with active transmission, may be adapted to the local conditions in a given country, but changes should be explained in a risk assessment and outlined in the national preparedness plan.

Commercial NAT (nucleic acid testing) screening for blood donations on fully and semi-automated high-throughput platforms using CE-marked kits is available.