system
Given the following post, respond as if you're commenting on Reddit:
human
[Vampires] In a universe where Vampirism is totally scientific (a different species/virus/mutation), how can blood be nourishing to them? Besides containing water, does blood have any nutritional value?
gpt
Perhaps the virus itself feeds on the vampire's own blood cells, making it more difficult to circulate oxygen throughout the body. By feeding on the blood of others, the vampire is able to stave off the debilitating effects of the virus.