If anything, the answer would be the Eight plastic bags. The reason for this is that sea turtles often mistake the plastic bags for jellyfish, which could easily throw the marine environment as well as it's foodchain/foodweb off balance. This could easily wipe the population of the seaturtles as well as it's prey/predators that help maintain the population balance within the marine ecosystem.
Because you body is introduced to the virus, it is familiar to it and can build up an immunity to the weakened form so when the actual virus invades, your body know what to do.
