In the United States, rotavirus can be serious but is rarely life threatening. Over fifty thousand children are admitted to the hospital each year due to rotavirus, and many more visit the emergency room, mostly for IV fluids until the virus runs its course. The vaccine information sheet for rotavirus mentions twenty to sixty deaths a year from the disease in the United States, so a death from rotavirus dehydration is an incredibly rare event.
Worldwide, however, where medical care is not adequate, hundreds of thousands of children die from dehydration from rotavirus each year. If IV fluids are not available, a child becomes severely dehydrated and dies before the body can recover.