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Dengue viruses causing severe, hemorrhagic disease have displaced less virulent strains in the Americas during the past three decades. The American (AM) genotype of dengue serotype 2 has been endemic in the Western Hemisphere and South Pacific, causing outbreaks of dengue fever (DF), but has not been linked to dengue hemorrhagic fever (DHF). The Southeast Asian (SEA) genotype of dengue was introduced into this hemisphere in 1981, has caused outbreaks with numerous cases of DHF, and has displaced the AM genotype in several countries. We investigated the effect of viral genotype on the potential for transmission by infecting Aedes aegypti mosquitoes collected in South Texas with six viruses, representing these two genotypes. Viral replication in the midgut was significantly higher in SEA-infected mosquitoes, and virus-specific proteins could be detected in salivary glands 7 days earlier in SEA- than AM-infected mosquitoes. This much earlier appearance of dengue virus in salivary glands resulted in an estimated 2- to 65-fold increase in the vectorial capacity of these mosquitoes for the viruses that can cause DHF. This may be one of the mechanisms through which more virulent flaviviruses spread and displace others globally.
Received March 15, 2006. Accepted for publication July 19, 2006.
Acknowledgments: The authors thank D. Bente for assistance in developing the RpS17 qRT-PCR assay, P. Armstrong for discussions of vectorial capacity, and R. Shade and M. Sharp for statistical consultation.
Financial support: This work was supported by Grant AI50123 from the National Institutes of Health.
* Address correspondence to Rebeca Rico-Hesse, Department of Virology & Immunology, PO Box 760549, Southwest Foundation for Biomedical Research, San Antonio, TX 78245-0549, Telephone: (210) 258-9681, Fax: (210) 258-9776, E-mail: rricoh{at}sfbr.org
Authors addresses: Justin R. Anderson and Rebeca Rico-Hesse, Department of Virology & Immunology, PO Box 760549, Southwest Foundation for Biomedical Research, San Antonio, TX 78245-0549, Telephone: (210) 258-9681, Fax: (210) 258-9776, E-mail: rricoh{at}sfbr.org
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