Généralités sur arbovirus et arboviroses

Arbovirus diseases are mainly tropical affections caused by a heterogenic group of viruses with common epidemiological properties. About 130 known arboviruses belonging to about 12 different virus families are of human or veterinarian medical importance. Many others are not pathogenic but can be interesting models for fundamental virological studies. Arboviruses survive in nature by biological transmission between vertebrate hosts and hematophage arthropoda. Arboviruses reproduce on these without change to their life or fecundity. They are transmitted through bite or sting of infected arthropoda to receptive vertebrates inducing an early and transitional viremia. A more or less complex cycle usually follows: virus, arthropoda vector, vector, vertebrate host. According to the vector’s ecology, each arbovirus is present in a specific area and is always likely to invade a non-endemic zone. The arthropoda in question are ticks, mosquitoes, phlebotomes, or Culicoides (Ceratopogonidae). Vertebrates either spread or amplify the viremia or they are accidental hosts or epidemiological dead-ends. Three types of clinical presentations are described: febrile polyalgia (“dengue-like” syndromes); hemorrhagic fever (frequently severe evolution); meningo-encephalitis (frequently severe evolution ending by death or recovery with severe neurological sequels). Various arboviruses are responsible for the same clinical presentations; but a same virus can induce several types of syndromes which stress the importance of laboratory diagnosis, based on the virus identification and specific serological tests. Prophylaxis relies on vaccination: yellow fever, tick borne encephalitis, Japanese encephalitis and fighting against vectors. New vaccines are being studied but not on the market yet.