Dengue and West Nile viruses are enveloped RNA viruses that belong to genus 
Flavivirus (family Flaviviridae) and are considered important mosquito-borne 
viral pathogenic agents worldwide. A potential target for intervention 
strategies is the virus cell entry mechanism. Previous studies of flavivirus 
entry have focused on the effects of biochemical and molecular inhibitors on 
viral entry leading to controversial conclusions suggesting that the process is 
dependent upon endocytosis and low pH mediated membrane fusion. In this study we 
analyzed the early events in the infection process by means of electron 
microscopy and immuno-gold labeling of viral particles during cell entry, and 
used as a new approach for infecting cells with viruses obtained directly from 
mosquitoes. The results show that Dengue and West Nile viruses may infect cells 
by a mechanism that involves direct penetration of the host cell plasma membrane 
as proposed for alphaviruses.