Preventing co-infection: a viral strategy with short-term benefits and long-term drawbacks

Viral co-infection occurs when multiple distinct viral particles infect the same host. This can impact viral evolution through intracellular interactions, complementation, reassortment and recombination. In nature many viral species are found to have a wide range of mechanisms to prevent co-infection, raising the question of how this strategic choice impacts viral evolution. We find that genetic drift is suppressed when co-infection is allowed, which in turn facilitates the fixation of beneficial mutations and the removal of deleterious ones. Interestingly, we also find that the growth rate (dis)advantage associated with variations in life history parameters can be dramatically different from the (dis)advantage measured in direct competition simulations. Finally, we find that a mutant which prevents co-infection displays a substantial competitive advantage over a co-infecting population even if it displays a much lower growth rate in isolation. Our findings suggest that while preventing co-infection can negatively impact the long-term evolution of a viral population, in the short-term it is ultimately a winning strategy.