Dengue virus particle, molecular model. This virus consists of an RNA (ribonucleic acid) genome surrounded by a protein nucleocapsid (cream), which is enclosed in an outer protein envelope (multicoloured). Set in the envelope are the E protein (red and yellow trimers), which has a role in the initial attachment of the virus to a host cell, and the M protein (black), which has a role in the formation of the virus particle. This virus, which is transmitted by mosquitoes, causes the tropical disease dengue fever. Symptoms can range from a mild fever and joint pain to spontaneous bleeding of the skin and circulatory failure, which are often fatal.