It's hard to say what the fatality rate for SAR-1 is, but it is certainly lower than the official CFR. Some individual clusters have <1%. Like SARS-CoV-2 ,SARS-1 and MERS CFR highly correlated with age, but there are some other factors that make little sense unless you consider terrorism with a dry aerosol BW. -a very high proportion of cases occur in nosocomial settings, other "super-spreader" incidents where dozens of people are infected at one time by one person -those having direct contact with a super-spreader have highest fatality rate -transmission chains are very short. Excluding super-spreaders, average number of secondary transmissions is ~0.1 -community spread is almost non-existent and these cases are mild You could infer that severity/fatality rate depends on the initial dose of aerosol you receive. This article looks at one well-known example, and briefly covers some of the downstream nosocomial outbreaks.