Patterns of Infection: Unwanted Guests—Quick Visits and Extended Stays

The preceding chapters describe essential aspects of viral pathogenesis, including virus–cell interactions; viral spread within a host; and intrinsic, innate, and adaptive immune responses. This chapter extends the theme and addresses diverse patterns of viral infections that are determined by both the virus and the host. Thus, virulence or susceptibility depends upon the specific virus–host combination. This is particularly true in the case of persistent infections, which involve a delicate balance between virus and host. We will focus first on virus virulence and host susceptibility, and then turn to the complex variables that govern persistent infections. Chapters 4–6, on innate, adaptive, and aberrant immunity, and Chapters 11–15, on systems biology approaches, also provide important insights into the patterns of infection.