Table 3.1.

Obligatory Steps in Viral Infection

Step in Infection Process	Requirement for Virus Survival and Progression of Infection
Entry into host and primary virus replication	Evade host’s natural protective and cleansing mechanisms
Local or general spread in the host, cell and tissue tropism, and secondary virus replication	Evade immediate host defenses and natural barriers to spread; at the cellular level the virus takes over necessary host-cell functions for its own replication processes
Evasion of host inflammatory and immune defenses	Evade host inflammatory, phagocytic, and immune defenses long enough to complete the virus transmission cycle
Shedding from host	Exit host body at site and at concentration needed to ensure infection of the next host
Cause damage to host	Not necessary, but this is the reason we are interested in the virus and its pathogenetic processes