Dengue virus infection. Animation of dengue virus particles (dark green) in the blood stream. This virus, transmitted by the bite of Aedes sp. mosquitoes, causes the tropical disease dengue fever in humans. This infection is causing the more serious dengue haemorrhagic fever, which causes the blood vessels to become permeable and leak blood plasma (orange). This can lead to spontaneous bleeding of the skin and circulatory failure, which are often fatal.