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Zika virus (ZIKV) is an emerging pathogen currently spreading in the Americas and responsible for microcephaly in some newborns. However, many aspects of the epidemiology of the virus and the natural history of infection still remain unknown.

A large study of volunteer blood donors - recently published in Blood - has been performed in Martinique Island (Caribbean region) during the local ZIKV outbreak in 2016 by Pierre Gallian and collaborators ("Emergence of Viral Pathogens unit", Marseille, France).

Systematic nucleic acid testing for the presence of the virus allowed the detection of approximately 2% of contaminated blood donations during the outbreak –and their subsequent exclusion to avoid blood-borne transmission. Identified by serological techniques, previous contact of blood donors with ZIKV revealed that a vast majority of ZIKV infections (over 80%) did not seek medical attention, highlighting the silent spread of the disease in the local population. In early June, more than 40% of the donors tested had been in contact with the virus. The authors also showed that, during the acute phase of infection, patients may have significant amounts of virus in their blood in the absence of clinical symptoms for approximately 6 days.

This pioneering study provides a precise follow-up of incident cases and seroprevalence in blood donors, and it also provides important insights into the management of blood donations during ZIKV outbreaks and into the natural history of ZIKV infection in adults. It suggests that the study of blood donors during outbreaks of emerging pathogens has become a key element of epidemiological surveillance.

This work was supported by Institut National de la Santé et de la Recherche Médicale (INSERM), Établissement Français du Sang (EFS), Institut de Recherche Biomédicale des Armées (IRBA), Institut de Recherche pour le Développement (IRD) and Aix-Marseille university (AMU). The research team is part of ZIKAlliance, a project funded by the European Union Horizon 2020 Research and Innovation Programme under Grant Agreement 734548 to better understand the clinical and fundamental aspects of infections by Zika virus (ZIKV).



For information about the scientific outputs of the paper, please contact Pierre Gallian at For more information about ZIKAlliance or ZIKAlliance’s activities, please contact Xavier de Lamballerie (Scientific Coordinator) at or phone: +33 491324420; or Flavia Mariani (Project Manager) at or phone: +33 491324412.