This will be an informal attempt to marshall my thoughts and seek help from workshop attendees.

The within-host reproductive rate of pathogens is a useful proxy for what are often called virulence tradeoffs. The faster a pathogen reproduces, the more attention it attracts from the host, leading to increased likelihood of morbidity, mortality or effective immune responses. Conversely, faster reproduction can lead to higher "titers" and more effective dispersal. Pathogens need to balance these tradeoffs at different levels. Pathogens such as rabies or anthrax, which spread by killing their hosts will see these tradeoffs differently, but may still seem them operate at the level of subpopulations.