In some species, e.g. sheep, different strains of prions exist. Discuss the experimental evidence for this observation and its molecular basis.
Some cancers are sexually transmitted diseases.
Expand this statement. Discuss the pathogenesis of plant virus infections with respect to the host response. Describe the epidemiology of human parvovirus infections and discuss how the pathology associated with this agent reflects its cellular requirements for replication. Describe in detail two of the viruses which cause human hepatitis.