Current mortality rate estimates for coronavirus disease 2019 (COVID-19) based on the number of deaths relative to the number of confirmed cases of infection may not be representative of the actual death rate, according to an correspondence analysis published in The Lancet.
Researchers re-estimated mortality rate with the caveat of an assumption that the denominator should be the total number of patients infected at the same time as those who died. However, because asymptomatic cases and/or untested patients cannot be identified, the full denominator remains unknown. Assuming a maximum incubation period of roughly 14 days, researchers re-estimated mortality rates by dividing the number of deaths on a given day by the number patients with confirmed COVID-19 cases 14 days prior.
Using World Health Organization data for the cumulative number of deaths as of March 1, 2020, researchers calculated a mortality rate of 5.6% (95% CI, 5.4-5.8) for patients in China and 15.2% (95% CI, 12.5-17.9) for patients outside of China. Using a 14-day delay estimate, global mortality rates level off at 5.7% (95% CI, 5.5-5.9), which converges with World Health Organization estimates.
“Estimates will increase if a longer delay between onset of illness and death is considered,” the researchers concluded. “A recent time-delay adjusted estimation indicates that mortality rate of COVID-19 could be as high as 20% in Wuhan, the epicenter of the outbreak. These findings show that the current figures might underestimate the potential threat of COVID-19 in symptomatic patients.”
Baud D, Qi X, Nielsen-Saines K, Musso D, Pomar L, Favre G. Real estimates of mortality following COVID-19 infection [published online March 12, 2020]. Lancet Infect Dis. doi:10.1016/S1473-3099(20)30195-X