Aquareoviruses are a genus of virus that infect fish, crustaceans, and shellfish and cause a range of pathological diseases. Some of these viruses, like the well-studied chum salmon reovirus (CSV), have little to no pathology to fish initially but can make them more susceptible to secondary infections that are often fatal. Other examples, like grass carp reovirus, cause hemorrhagic disease that can be lethal. Since the death of fish poses a significant impact to both aquatic diversity and the fishing economy, it is important to understand the host-pathogen interactions surrounding these fish-infecting viruses. Current research hypothesizes that microorganisms, like ciliates, could act as concentrators of viruses in aquatic environments. Tetrahymena are a model ciliate that we are using to study aquatic viral transmission because they are easy to culture and there are readily available genetic tools to study them. T. thermophila is already known to increase the infectivity of CSV. My hypothesis is that T. thermophila similarly causes the increase of infectivity of all aquareoviruses. To test this hypothesis, we incubated T. thermophila with four different aquareoviruses, including CSV, overnight. From there, we can measure the viral titer, or level of infectivity, of the virus and compare it with CSV. Preliminary data suggest that the opposite of our hypothesis is true. We saw lower viral titer from 13p2 and Green River aquareoviruses when exposed to Tetrahymena, suggesting that the ciliates might eliminate the virus, not increase its infectivity. Future research will expand this study to encompass more species of Tetrahymena that are available and will look into the nature of the aquareoviruses themselves. This knowledge can be applied further to current work being done in our lab on zebrafish- aquareovirus interactions as well. This research will continue to fill the gap in the knowledge of these ciliate/aquatic virus interactions while also opening the door for future studies of viruses with Tetrahymena.