Dengue is an endemic viral disease present in inter-tropical countries. If dengue is usually benign, more severe forms (severe dengue [SD]) may lead to serious complications. The prognosis of SD is currently unreliable. To improve the prognosis, it could be necessary to knowthe key elements of the pathogenicity of the SD. Many hypotheses have been developed to explain a higher pathogenicity in SD patients. Numerous studies have highlighted the role of the host immune response and of the infecting virus strain. The development of these hypothesis allows to have a better understanding of the pathogenesis and consequently, to provide prognostic candidate-markers of SD, these markers being either associated with the host or with the virus. The present review proposes to paint a non-exhaustive picture of the most important hypothesis of dengue pathogenicity as well as potential prognostic markers of severe forms of dengue.