Abstract
The Zika virus, named after the Ugandan forest where it was first identified in 1947, has long remained an exotic curiosity. Transmitted by Aedes mosquitoes, it circulates endemically in sub-Saharan Africa and Southeast Asia, and appears to be benign. In 2007, it appeared on the island of Yap in Micronesia, before spreading to French Polynesia in 2013-2014. There, it infected more than half the population, causing a large number of severe paralyses known as Guillain-Barré syndromes. In 2015, during a massive epidemic in Brazil, children born to mothers infected during pregnancy were found to suffer severe neurological abnormalities, including microcephaly. On February1 2016, the WHO declares Zika " a public health emergency of international concern ", and calls on the scientific community to mobilize to establish the link between the Zika virus and the neurological complications observed in adults and babies.
While several virological studies document the greater permissiveness of neural progenitor cells, those that between the sixth and tenth weeks of development will give rise to the future brain, a cohort study in the West Indies involving 546 pregnant women estimates the risk of birth defects in children born to mothers infected with the Zika virus during pregnancy at 7 %. The risk is highest for infections occurring in the first trimester of pregnancy. The epidemic came to a halt at the end of 2016, due to a lack of fighters, after sweeping across the Pacific Islands, Latin America, Central America, and the West Indies. In the hardest-hit areas, more than half the population has been infected, so a new epidemic is unlikely until the pool of people likely to be infected is replenished. At the end of this epidemic, there is still no cure for the Zika virus. Several vaccines are currently under development, but are unlikely to be tested in phase 3 in the absence of an epidemic. Vector studies have shown the predominant role played by Aedes aegypti in transmission. Aedes albopictus is a competent vector in the laboratory, but has not been incriminated " in the field ". This epidemic has shown the limits of traditional vector control approaches (destruction of breeding sites, intra-domiciliary spraying and use of repellents) and calls for innovative approaches (e.g. mosquitoes infected with Wolbachia bacteria or genetically modified mosquitoes) to control Aedes mosquitoes, which are responsible not only for the transmission of the Zika virus, but also of yellow fever, dengue and chikungunya viruses.
