Multi-pathogen infections occur in many systems, and the diversity of infections can affect the spread and intensity of disease. The composition of pathogen communities is mediated by their host environment, interactions with one another, and modes of transmission. We used laboratory experiments to investigate the roles of soil nitrogen and phosphorus on the growth of two viruses within a plant host. In addition, we measured transmission success to evaluate the potential for within-host processes to scale up and affect the disease dynamics among hosts.
Results/Conclusions
We found that nutrients affected the growth of one of the viruses within the plant, and that co-infection had occasional positive effects on growth, which varied with timing and nutrient. Contrary to within-host results, co-infection tended to reduce transmission success. In addition, the population sizes of viruses within the host did not strongly affect transmission success, a common assumption. Our results indicate that nutrient effects are pathogen-specific, even for ecologically similar viruses, and within-host processes do not directly scale up to predict transmission success.