Evidence of Zika virus circulation in human and livestock in Chad.

Zika virus (ZIKV) is a major public health problem worldwide. After several reported outbreaks, the current extent of infections caused by this orthoflavivirus in the Sahel remains to be explored. We investigated the prevalence of neutralizing antibodies against ZIKV in the general population, in HIV-infected individuals and in livestock in Chad using a seroneutralization assay that ensures high specificity level. In this retrospective serological serosurveillance investigation, we estimated the neutralizing seroprevalence to be approximately 26 % (18/69) in healthy Chadian participants and 17 % (16/94) in HIV-infected individuals, with no statistical difference between these two subgroups or genders. In addition, we found an overall ZIKV prevalence of 14 % (8/59) in small ruminants (sheep and goats) living in the Lake Chad Basin area, demonstrating virus circulation in animals. Our pilot study shows for the first-time evidence of ZIKV circulation in humans and in livestock in Chad in close interaction with humans, and highlights the main challenges associated with this virus in Sahelian areas.