Research in the Hardy laboratory is focused on the molecular requirements for virus replication. We are specifically interested in what molecules are necessary for the replication of the viral genetic material and the optimal expression of viral genes within host cells. Viruses present a unique challenge to the understanding of their replication because of their obligate, intracellular, parasitic nature; that is, they can only replicate inside a host cell and require numerous cellular resources in order to proliferate. This intimate, though parasitic, relationship with the host cell means that we must look to both viral and host components to understand virus replication. For certain viruses the problems are of even greater complexity since they infect multiple host species. Many viruses, such as those causing human diseases like Dengue fever and yellow fever, are transmitted by mosquitoes. These viruses cause devastating disease in humans; however, the mosquito shows little or no adverse effects as a consequence of infection. We infer that such viruses interact with the vertebrate and arthropod hosts in very different ways.