Case fatality rates (CFR) are used to describe the proportion of those infected that died from the disease compared to the total number of those who acquired the infection. In the case of SARS-CoV, the global average case fatality rate was estimated to be 15% by the WHO. However, it was also estimated that the CFR for patients younger than 60 years of age was 6.8%, while the CFR for patients older than 60 years was 55%. This shows that there is much variation in the mortality rate between age groups.