  The canonical bacteriophage is obligately lytic: the virus infects a
bacterium and hijacks cell functions to produce large numbers of new viruses
which burst from the cell. These viruses are well-studied, but there exist a
wide range of coexisting virus lifestyles that are less understood. Temperate
viruses exhibit both a lytic cycle and a latent (lysogenic) cycle, in which
viral genomes are integrated into the bacterial host. Meanwhile, chronic
(persistent) viruses use cell functions to produce more viruses without killing
the cell; chronic viruses may also exhibit a latent stage in addition to the
productive stage. Here, we study the ecology of these competing viral
strategies. We demonstrate the conditions under which each strategy is
dominant, which aids in control of human bacterial infections using viruses. We
find that low lysogen frequencies provide competitive advantages for both virus
types; however, chronic viruses maximize steady state density by eliminating
lysogeny entirely, while temperate viruses exhibit a non-zero `sweet spot'
lysogen frequency. Viral steady state density maximization leads to coexistence
of temperate and chronic viruses, explaining the presence of multiple viral
strategies in natural environments.
