Virus, Vector, Vertebrate

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Science  03 Aug 2001:
Vol. 293, Issue 5531, pp. 763
DOI: 10.1126/science.293.5531.763a

The flaviviruses are responsible for many diseases of significance to humans. Gaunt et al. have used sequence data to construct phylogenetic trees to help define the complex interrelationships between the viruses, their hosts, and the diseases they cause.

The flaviviruses fall into three major clades: mosquito-borne, tick-borne, and those with no known vectors. Hence, it seems the Aedes spp. of mosquitoes are associated with the primate hemorrhagic diseases, including dengue and yellow fevers, which reflects the slightly fussy feeding habits of this mosquito genus. The Culex spp. group appears to have evolved later than the Aedes group and are indiscriminate feeders transmitting neurotrophic viruses, including West Nile fever and Japanese encephalitis among mammals and birds. In contrast, the tick-borne viruses do not divide into disease groups, but the shift to the universal vector Ixodes has hit economically important targets, as with louping ill virus in sheep.

It appears that the out-of-Africa notion also holds true for the flaviviruses, and it is probable that yellow fever and dengue crossed the Atlantic on slave ships. Gaunt et al. hope that this kind of analysis will offer a tool not just for tracing the history of these viruses, but for predicting and monitoring the emergence of new viral diseases. — CA

J. Gen. Virol.82, 1867 (2001).

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