I was assuming a household of 4, living together, who all came down with the disease and each had a probability of 25% of dying from it.
In reality, there is a pretty good chance that if one person in a family living together gets SARS, the other ones will get it as well. It is like flu or measles or chicken pox in that regard. However, it is true that not all would come down.
Age has a big impact as well. If it is a pair of parents in their 30s with two small children, the children are very likely to survive and the parents have only a 1 or 2 percent chance of dying, assuming they aren't immunosupressed or have other medical conditions.
If it is adult children (50s) living with aged parents (70s or 80s), the odds are pretty good that both aged parents die and that at least one of the children dies as well.
Loosed in a senior citizen's home, SARS would empty the place.
No question that would be a tragic situation. The spread in hospitals isn't that surprising either, considering that most hospitalized people are in a weakened state too.
The spread among hospital workers is somewhat surprising to me though.