The dengue or tropical flu virus, which is rife mainly in the intertropical zone, belongs to the flavivirus family, such as the Zika virus, yellow fever, West Nile, etc. They are arboviruses (short for arthropod-borne viruses), because they have the particularity of being transmitted by arthropods, blood-sucking insects like mosquitoes. There are four different types (or serotypes) of dengue virus, with specific immunity for each subtype, but no cross-immunity between the 4 subtypes. This means that one cannot be contaminated a second time by a virus of the same serotype, but that it is possible to contract dengue fever due to one of the other three types. According to a hypothesis supported by the WHO, a second contamination with another serotype exposes a ten times greater risk of developing a severe form than during a first infection, but this theory is currently disputed by many experts. Dengue is the most common human arbovirus with 50 to 100 million cases per year worldwide. Its incidence has multiplied by 30 in fifty years. The dengue virus has long remained confined to Southeast Asia, before spreading to the Indian Ocean, the Pacific, South America, Central America, the Caribbean, but continues to expand due to anarchic urban development, the increase in international trade and climate change. The virus is particularly widespread in the French departments of America (Guyana, Guadeloupe, Martinique) as well as in Polynesia, New Caledonia, in Mayotte on the island of Reunion.