Dengue virus vaccine. Animation of dengue virus particles (blue, green, yellow and pink) being injected into the skin. All four strains of the dengue virus are being injected. They will infect dendritic cells (cream), a component of the body's immune system, eliciting a protective immune response. Dendritic cells are antigen-presenting cells (APCs), that is, they present pathogens or foreign molecules (antigens) to other cells of the immune system to be eliminated. Dengue virus, transmitted by the bite of Aedes sp. mosquitoes, causes the tropical disease dengue fever in humans. Symptoms can range from a mild fever and joint pain to spontaneous bleeding of the skin and circulatory failure, which are often fatal.