SARS may be frightful, but the fact is that some people are unaffected by a virus no matter how ferocious it may be, and will not become seriously ill. Look for example at the enterovirus-71 epidemic in 1998.
別看 SARS 令人聞之色變，事實上，再怎麼凶猛的病毒也有人可以不為所動，不會引發重大病徵，這也就是所謂的「隱性患者」。