European and tropical Aedes albopictus mosquito populations have similar systemic Zika virus infection dynamics

First isolated from a forest in East Africa in the mid-20th century, Zika virus (ZIKV) has now emerged worldwide in urbanized areas where its mosquito vectors, mainly Aedes aegypti and Ae. albopictus, are present. Europe and French overseas territories in the Indian Ocean have been so far spared despite the presence of Ae. albopictus, the Asian tiger mosquito. However, because they have strong economic and touristic links with regions affected by ZIKV, French territories in the Indian Ocean have a high risk of introduction. Here, we assess the susceptibility of two Ae. albopictus populations from Metropolitan France and the Reunion island (a French oversea territory in the Indian Ocean) for a ZIKV isolate from the Asian genotype at a titer ranging from 3 to 7.5 x 106 focus-forming units per milliliter. High infection rates and unpreceded levels of systemic infection rates were observed in both Metropolitan France and the Reunion island populations, without differences in infection rates or intra-mosquito systemic infection dynamics between the two mosquito populations. Ten and 20-days were needed by the virus to disseminate in 50% and 100% of the exposed mosquitoes respectively. Such slow intra-mosquito viral dynamics, in addition to repeatedly reported high transmission barrier in the literature, can impact ZIKV transmission when potentially vectored by Ae. albopictus. However, because mosquito-borne virus intra-host transmission dynamics can be influenced by numerous factors, including virus dose dynamics inside infectious humans or viral evolution towards shorter extrinsic incubation periods (EIP), our results highlight that Ae. albopictus populations present in Metropolitan France and the French territoires in the Indian Ocean might become potential vector for autochthonous ZIKV transmissions.