Dengue viruses are transmitted from person to person by Aedes (Ae.) mosquitoes of the subgenus Stegomyia. Ae. aegypti is the most important epidemic vector, but other species such as Ae. albopictus, Ae. polynesiensis, members of Ae. scutellaris complex, and Ae. (Finlaya) niveus have also been incriminated as secondary vectors. All except Ae. aegypti have their own restricted geographical distribution and, although they may be excellent hosts for dengue viruses, they are generally less efficient epidemic vectors than Ae. aegypti.