Polio is also classified as an enterovirus. Although the disease can be deadly, it, too, can affect different patients differently. Some have even suggested that there is a genetic component that makes some more susceptible than others. My cousin had six children, all in the days before the development of the vaccine. Every other child had polio, even though, obviously, they were all grew up in the same household and were exposed to much the same environment outside of their home.
There could be a genetic susceptibility to bad results from enteroviruses, but there is definitely a difference between a robust immune system and a typical weak one.