Hawaii health officials reported three additional dengue fever cases on Big Island Tuesday, which brings the total of dengue local transmission in this outbreak to 213 since the first case was reported on Oct. 21.

Image/National Atlas of the United States
Image/National Atlas of the United States

In addition, since the beginning of our current investigation on Hawaii island, six imported dengue fever cases have been confirmed (four on Oahu, one on Maui, and one on Hawaii), and one imported chikungunya case (on Hawaii) has been confirmed. These cases are not associated with the Hawaii island investigation.

Through the middle of December, the United States saw 576 dengue fever cases with three-quarters of the cases being classified as travel associated.

Dengue is a mosquito-borne viral disease spread from human to human via mosquitoes. No important non-human reservoir exists. Approximately 100 million dengue illnesses occur each year in endemic countries throughout the tropical world.

Dengue virus is spread primarily by Aedes aegypti (yellow fever mosquito), an aggressive urban, human biting mosquito, which typically feeds indoors. In the Hawaiian Islands, Aedes aegypti is thought to be endemic only in certain areas on the Island of Hawaii, including the Kona Coast.

In contrast, Aedes albopictus (Asian tiger mosquito) is widely prevalent throughout the Hawaiian Islands. Compared with Aedes aegypti, Aedes albopictus thrives in less urban habitats and transmits dengue less efficiently because it feeds on many other animals besides humans.

Dengue has not become endemic to the Hawaiian Islands despite frequent introductions from infected travelers. However, introductions have occasionally resulted in outbreaks; the last major outbreak involved 122 laboratory-confirmed cases with disease onsets over a 9-month period in 2001 and 2002.