The first reports of major epidemics of an illness thought to possibly be dengue occurred on three continents (Asia, Africa and North America) in 1779 and 1780 (Rush 1789, Hirsch 1883, Pepper 1941, Howe 1977). However, reports of illnesses compatible with dengue fever occurred even earlier. The earliest record found to date was in a Chinese 'encyclopaedia of disease symptoms and remedies,' first published during the Chin Dynasty (AD 265 to 420) and formally edited in AD 610

(Tang Dynasty) and again in 992 during the Northern Sung Dynasty (Nobuchi 1979). Outbreaks of illness in the West Indies in 1635 and in Panama in 1699 could also have been dengue (Howe 1977, McSherry 1982). Thus, a dengue-like illness had a wide geographic distribution before the 18th century, when major epidemics of dengue-like illness occurred widely. It is uncertain that the epidemics in Batavia (Jakarta), Indonesia, and Cairo, Egypt, in 1779 were actually dengue (Carey 1971).

At some point in the past, probably with the clearing of the forests and development of human settlements, dengue viruses moved out of the jungle and into a rural environment, where they were, and still are, transmitted to humans by peri-domestic mosquitoes such as Aedes albopictus. Migration of people and commerce ultimately moved the viruses into the villages, towns, and cities of tropical Asia, where the viruses were most likely transmitted sporadically by Aedes albopictus and other closely related peridomestic Stegomyia mosquito species.

The slave trade between West Africa and the Americas, and the resulting commerce, were responsible for the introduction and the widespread geographic distribution of an African mosquito, Aedes aegypti, in the New World during the 17th, 18th and 19th centuries. This species became highly adapted to humans and urban environments and was spread throughout the tropics of the world by sailing ships. The species first infested port cities and then moved inland as urbanization expanded. Because Ae. aegypti had evolved to become intimately associated with humans, preferring to feed on them and to share their dwellings, this species became a very efficient epidemic vector of dengue and yellow fever viruses (Gubler 1997). Therefore, when these viruses were introduced into port cities infested with Ae. aegypti, epidemics occurred. It was in this setting that major epidemics of dengue fever occurred during the 18th, 19th and early 20th centuries, as the global shipping industry developed and port cities were urbanized in response to increased commerce and ocean traffic. The last major dengue pandemic began during World War II and continues through the present (Gubler 1997, Halstead 1992).

The earliest known use of the word dengue to describe an illness was in Spain in 1801 (Soler 1949). However, the most likely origin of the word is from Swahili (Christie et al 1872, Christie 1881). In both the 1823 and 1870 epidemics of denguelike illness in Zanzibar and the East African coast, the disease was called Ki-Dinga pepo. From this came the name dinga or denga, which was used to describe the illness in both epidemics. Christie (Christie et al 1872, Christie 1881) speculates that the name denga was taken via the slave trade to the New World, where it was called 'Dandy fever' or 'The Dandy' in the St. Thomas epidemic of 1827. The illness was first called dunga in Cuba during the 1828 epidemic, but later changed to dengue, the name by which it has been known ever since (Munoz 1828). Most likely, the Spanish recognized the disease in Cuba as the same one that was called dengue in Spain in 1801. If the word dengue did originate in East Africa from dinga or denga, this suggests the disease was occurring before the 1823 epidemics described by Christie. This is not unlikely since epidemics were reported in Africa, the Middle East and Spain in the late 1700s.

With documentation that yellow fever was transmitted by mosquitoes, many early workers suspected that dengue fever was also mosquito-borne. In the previ-rology era, work was slow and relied on use of human volunteers. Work done by Graham (1903), Bancroft (1906) and Cleland et al (1918) documented dengue transmission by mosquitoes.

Although it had been shown that dengue fever was caused by a filterable agent, (Ashburn et al 2004, Siler et al 1926) the first dengue viruses were not isolated until the 1940s, during World War II (Kimura & Hotta 1944, Hotta 1952, Sabin & Schlesinger 1945, Sabin 1952). Dengue fever was a major cause of morbidity among Allied and Japanese soldiers in the Pacific and Asian theatres. Sabin and his group were able to show that some virus strains from three geographic locations (Hawaii, New Guinea and India) were antigenically similar (Sabin & Schlesinger, Sabin 1952). This virus was called dengue 1 (DENV-1), and the Hawaii virus was designated as the prototype strain (Haw-DENV-1). Another antigenically distinct virus strain isolated from New Guinea was called dengue 2 (DENV-2), and the New Guinea C strain (NGC-DENV-2) was designated the prototype. The Japanese virus isolated by Kimura and Hotta (Kimura & Hotta 1944, Hotta 1952) was subsequently shown to be DENV-1 as well. Two more serotypes, dengue 3 (DENV-3) and dengue 4 (DENV-4), were later isolated from patients with a haemorrhagic disease during an epidemic in Manila, in 1956 (Hammon et al 1960). Since these original isolates were made, thousands of dengue viruses have been isolated from all parts of the tropics; all have fit into the four-serotype classification.

The occurrence of severe and fatal haemorrhagic disease associated with dengue infections is not unique to the twentieth century. Patients with disease clinically compatible with dengue haemorrhagic fever (DHF) have been reported sporadically since 1780, when such cases were observed in the Philadelphia epidemic (Rush 1789). Significant numbers of cases of haemorrhagic disease were associated with several subsequent epidemics, including Charters Towers, Australia, in 1897, Beirut in 1910, Taiwan in 1916, Greece in 1928 and Taiwan in 1931 (Copanaris 1928, Akashi 1932, Halstead & Papaevangelou 1980, Rosen 1986, Hare 1898, Koizumi et al 1916). However, epidemic occurrences such as these were relatively rare, and the long intervals between them made each a unique event that was not considered important in terms of a long-term, continuous public health problem. Understanding the emergence of dengue and DHF as a global public health problem in the last half of the 20th century requires a review of the ecological and demographic changes that occurred in the Asian and American tropics during this period. The detailed history of dengue has been recently reviewed (Gubler 1997).

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