Dengue virus is a small single-stranded RNA virus in the Flaviviridae family. It is a 50 nm enveloped virus. There are four serotypes (DEN-1 to -4). More severe disease is seen with serotypes 2 and 3, which are primarily found in Asia. Immunity is type specific; a person can be infected more than once with a different serotype.
Infection occurs through a bite of the infected Aedes mosquito, most frequently Ae. aegypti. This mosquito is found worldwide in lower altitudes, below 1,000 meters. Ae. albopictus, Ae. polynesiensis, and several species of the Ae. scutellaris complex can also spread dengue in other ecologies. Ae. albopictus has spread from Asia to Africa and to the Americas and Europe primarily through automotive tires, where eggs were deposited in water held in them. Mosquito eggs can survive months in dried out tires. Ae. albopictus was the vector for a small outbreak in Hawaii in 2001.
Image showing examination of tire for mosquito larvae. Courtesy of the CDC.