Basic Concepts: A Step-by-Step Guide to Viral Infection

Viral pathogenesis seeks to understand how a virus interacts with its host at multiple levels. Key questions include the source (an infected human, animal, or insect vector), the transmission mechanism, and how the virus is shed and transmitted. Following transmission, pathogenesis is governed by the initial site of replication, whether the virus disseminates within the host, and its tropism for specific tissues and organs. In turn, these steps are dictated by the structure and replication strategy of the virus. In addition to utilizing selected synthetic biochemical pathways in the host cell, viruses frequently reprogram host cells by inducing intracellular signaling pathways that render the cell more permissive. Host–virus interactions also control whether the infection is acute, chronic, latent, or transforming; how the virus interacts with the immune system; and the consequent pathophysiological response of the host. This chapter provides an overview of these basic concepts of viral pathogenesis, with emphasis on the interactions of viruses with their host cells and organisms.