Why Epidemiologists Still Don’t Know the Death Rate for Covid-19

Determining what percentage of those infected by the coronavirus will die is a key question for epidemiologists, but an elusive one during the pandemic.

“Coroners in some parts of the country are overwhelmed. Funeral homes in coronavirus hot spots can barely keep up. Newspaper obituary pages in hard-hit areas go on and on. Covid-19 is on track to kill far more people in the United States this year than the seasonal flu.

But determining just how deadly the new coronavirus will be is a key question facing epidemiologists, who expect resurgent waves of infection that could last into 2022.

As the virus spread across the world in late February and March, the projection circulated by infectious disease experts of how many infected people would die seemed plenty dire: around 1 percent, or 10 times the rate of a typical flu.

But according to various unofficial Covid-19 trackers that calculate the death rate by dividing total deaths by the number of known cases, about 6.4 percent of people infected with the virus have now died worldwide.

In Italy, the death rate stands at about 13 percent, and in the United States, around 4.3 percent, according to the latest figures on known cases and deaths. Even in South Korea, where widespread testing helped contain the outbreak, 2 percent of people who tested positive for the virus have died, recent data shows.

These supposed death rates also appear to vary widely by geography: Germany’s fatality rate appears to be roughly one-tenth of Italy’s, and Los Angeles’s about half of New York’s. Among U.S. states, Michigan, at around 7 percent, is at the high end, while Wyoming, which reported its first two deaths this week, has one of the lowest death rates, at about 0.7 percent.

Virology experts say there is no evidence that any strain of the virus, officially known as SARS-CoV-2, has mutated to become more severe in some parts of the world than others, raising the question of why there appears to be so much variance from country to country.

Coffins were transported in Italy, where 12.8 percent of people with confirmed infections have died.

Determining death rates is especially challenging in the midst of a pandemic, while figures are necessarily fluid. Fatality rates based on comparing deaths, which are relatively easy to count, to infections, which are not, almost certainly overestimate the true lethality of the virus, epidemiologists say. Health officials and epidemiologists have estimated there are five to 10 people with undetected infections for every confirmed case in some communities, and at least one estimate suggests there are far more.”