Aedes aegypti is an effective vector of yellow fever, and both mosquito species are effective vectors of dengue. The extrinsic incubation period of dengue and yellow fever viruses is shortened by higher ambient temperatures, leading to more rapid amplification of epidemic spread. All four serotypes of dengue virus have been introduced into the United States in recent years, and introduction is a regular occurrence that can be expected to continue. There is no vaccine for dengue. Cholera Let me turn now to a very different disease, cholera.
Cholera behaves ecologically, however, like a three-factor complex.
Cholera is characterized by profuse, watery diarrhea leading to loss of body salts and severe dehydration. The disease is rapidly fatal in a high percentage of patients if fluid and salt replacement is not immediately available. The causative agent of epidemic cholera is a bacterium, Vibrio cholerae serogroup 01, that is motile and grows aerobically at 37deg. C. Cholera has been known for centuries in the delta of the Brahmaputra and Ganges rivers. Since the beginning of the nineteenth century there have been seven pandemics in which the Vibrio cholerae spread rapidly from endemic foci, usually in Asia, to Africa, Europe, and sometimes to North America.