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Arbovirus dissemination from the midgut of a vector mosquito is a critical step in facilitating virus transmission to a susceptible host. We previously characterized the genetic determinants of yellow fever virus (YFV) dissemination from the Aedes aegyptimosquito midgut using 2 genetically and phenotypically distinct strains of YFV the wild-type, disseminating YFV Asibi strain and the attenuated, midgut-restricted YFV 17D vaccine strain. We examined the process of viral dissemination in YFV-infected Ae. aegyptiby characterizing the tissue tropisms of 3 YF viruses in Ae. aegyptiAsibi, 17D, and a chimeric virus (17DAsibi M-E) containing the Asibi membrane (M) and envelope (E) structural protein genes and 17D nonstructural genes. Ae. aegyptiwere infected orally, and whole, sectioned mosquitoes were evaluated for antigen distribution at 3, 7, 10, 14, and 21 days postinfection by immunohistochemical staining. Virus antigen was consistently observed in the posterior and anterior midgut, cardial epithelium, salivary glands, fat body, and nervous tissues in Asibi- and 17DAsibi M-E-infected Ae. aegyptifollowing 10 or 14-day extrinsic incubation, respectively. Amplification of virus in the abdominal and thoracic fat body is hypothesized to facilitate YFV infection of the Ae. aegyptisalivary glands. As expected, 17D infection was generally limited to the midgut following oral infection. However, there did not appear to be a direct correlation between distribution of infection in the midgut and dissemination to the secondary tissues. [ABSTRACT FROM AUTHOR]