Likelihood of survival of coronavirus disease 2019 - The Lancet
By: S. Ruan
Estimate case fatality ratio for covid-19
- Case fatality ratios (cfr) measure the proportion of all individuals diagnosed with a disease who die from that particular disease. It indicates disease severity and its significance as a public health problem.
- As of March 21, 2020, there have been 292 142 confirmed cases of COVID-19 worldwide, with 12 784 deaths reported.
- A Chinese study of 1100 patients estimated cfr at 1.4%. Another Chinese studies reported 2.3% and 3.8% cfr respectively in 44672 and 55924 patients and pointed out it varied in regions, month, age, presence of comorbidities and sex.
- Simply dividing the number of deaths by the number of cases is misleading because of the 2-3 weeks incubation and detection period. In addition, mostly only severe cases are identified.
- Another Lancet study (https://doi.org/10.1016/S1473-3099(20)30243-7) estimated time from symptom onset to death to be 17.8 days. From symptoms to hospital discharge: 24.7 days. They estimated an adjusted cfr of 1.38% in China which increases with age.
- Estimates of case fatality ratios might vary slightly from country to country because of differences in prevention, control, and mitigation policies implemented, and because the case fatality ratio is substantially affected by the preparedness and availability of health care.
- Cfr comparison between covid19 and influenza shows covid is in no way comparable to influenze (see figure). Even for youngsters mortality is 33 times higher.
- Evidence shows early detection and prevention of spread also lowers cfr.