COVID-19's Death Rate: Why It Can Be as High as 12% or as Low as 0.25%
Two studies published last Friday to the journal Emerging Infectious Diseases, which is maintained by the Centers for Disease Control and Prevention, attempted to calculate the risk of death from COVID-19, the disease caused by the SARS-CoV-2 coronavirus. In doing so, the researchers behind the reports showcased the best- and worst-case scenarios for the pandemic.
Dr. Kenji Mizumoto of Kyoto Unviersity and Dr. Gerardo Chowell from Georgia State University examined the time-delay adjusted risk for death in China from the beginning of the outbreak through February 11th. The time-delay adjustment attempts to account for the underestimation in death rate caused by the gap in illness onset to death between the vulnerable population and the healthy population. They found that in the early stages of the outbreak the risk of death from COVID-19 reached 12.2% in Wuhan, China, the disease's epicenter. As you might recall, Wuhan's medical system was completely overrun in the early stages of the outbreak, forcing the government to build two hospitals in just over a week. The construction of these facilities, coupled with containment measures like quarantines and isolation, drastically reduced the cases and death rate from COVID-19 in the weeks since. For someone in Wuhan with the disease today, their risk of death is now likely comparable to the risk of death for someone living outside of Hubei Province in China, which stood at 0.9 percent or lower as of a month ago.
In the second study, researchers at the University of Otago Department of Public Health in Wellington, New Zealand used worldwide case and fatality data from the World Health Organization through March 5th to discern a death rate range for COVID-19. Like Mizumoto and Chowell, they tried to adjust for the time lag from case report to death or recovery.
"Health sector decision-makers and disease modelers probably should consider a broad range of 0.25%–3.0% for COVID-19 case-fatality risk estimates," they wrote. "The higher values could be more appropriate in resource poor settings where the quality of hospital and intensive care might be constrained. Higher values might also be appropriate in high-income countries with limited surge capacity in hospital services because elevated case-fatality risks could be seen at the peak of local epidemics."
In both studies, the scientists acknowledge that fatality rates could be significantly inflated due to both a lack of testing and mild cases that go unreported. We may not know the true overall death rate for months to come, but experts are optimistic that it will be at the low end of estimates – likely less than two, or even one, percent.
Now that the coronavirus is spreading globally, with 169,175 confirmed cases and 6,499 deaths as of March 15, all governments and peoples essentially face a choice between the worst-case scenario witnessed early on in Wuhan and the best-case scenario in a country like Singapore, where the death rate is zero. Mass testing, tracking, social isolation, and containment, as we've seen in South Korea and Singapore, can cap the number of cases at manageable levels and keep the death rate at 1% or lower. Complacency, as we've seen in Italy (which currently has a 7.7% crude death rate), Iran (exact death rate unknown, presumably very bad), and (arguably) the United States, can have disastrous, deadly consequences and force draconian actions once an outbreak spins out of control.
As Chowell and Mizumoto wrote:
"Because the risk for death from COVID-19 is probably associated with a breakdown of the healthcare system in the absence of pharmaceutical interventions (i.e., vaccination and antiviral drugs), enhanced public health interventions (including social distancing measures, quarantine, enhanced infection control in healthcare settings, and movement restrictions), as well as enhanced hygienic measures in the general population and an increase in healthcare system capacity, should be implemented to rapidly contain the epidemic."
Mizumoto K, Chowell G. "Estimating risk for death from 2019 novel coronavirus disease, China, January–February 2020." Emerg Infect Dis. 2020 Jun. https://doi.org/10.3201/eid2606.200233
Wilson N, Kvalsvig A, Telfar Barnard L, Baker MG. "Case-fatality estimates for COVID-19 calculated by using a lag time for fatality." Emerg Infect Dis. 2020 Jun. https://doi.org/10.3201/eid2606.200320