Coronavirus Death Rate Will Largely Be a Mystery Until the Pandemic Ends

With the death toll of the coronavirus nearing 200,000, according to Johns Hopkins University, it is clear that the bug fueling the COVID-19 pandemic is deadly. But experts told Newsweek that the deadliness of the disease can only be accurately quantified after the pandemic. So far, COVID-19 has killed over 191,000 people in more than 2.5 million diagnosed cases, with more than 745,000 survivors reported by health officials. As shown in the Statista graph below, the U.S. has the most known COVID-19 cases.

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That phrase, "known COVID-19 cases," highlights part of the problem with uncovering a person's risk of dying from the disease. There are a few ways that epidemiologists look at how deadly a condition is. These include what are known as the infection fatality rate and the case fatality rate. Firstly, it is important to note a range of factors can cause these changeable numbers to rise and fall, from the health and circumstances of the individual infected to how many people are accurately tested in the population in question. The strength of the healthcare system also plays a part, as does whether deaths are correctly documented. The figure best-suited to understanding the virus is the infection fatality rate, or the percentage of people who die after catching the coronavirus, according to the University of Oxford-based team behind the Our World in Data website. That value is calculated by taking the total number of deaths from any given disease divided by the total number of sick people. For instance, if 500 people have a disease and 10 die, the infection fatality rate would be 2 percent. But it is "just not possible or arguably necessary to test every single person who might have the disease nor do all patients actually report that they have disease symptoms," Mark Fielder, professor of medical microbiology at England's Kingston University, told Newsweek. As such, when lay people talk about the death or mortality rate of the coronavirus, we're actually referring to the case fatality rate. This is calculated by dividing the number of people known to have died from a disease by the total number of people who have been diagnosed and officially documented by a healthcare professional.

The case fatality rate is currently skewed by what epidemiologists call the severity bias, Steffanie Strathdee, associate dean of global Health sciences at University of California San Diego, told Newsweek. As many countries have still not reached the peak of their outbreaks and their health systems are overwhelmed, the serious cases are diagnosed first, she said. If the cases most likely to die make up a large chunk of those officially recorded, this can make the coronavirus appear more deadly than it is. The infection fatality rate of coronavirus is therefore "likely to be significantly lower" than the case fatality rate, because tests are limited and largely available to people with serious cases of and risk factors for COVID-19, and because many coronavirus infections result in undocumented mild or symptomless cases, professor Rich Condit, a virologist at the University of Florida, explained on the Virology.ws blog. As the virus continues to spread, the case fatality rate can represent an overestimate or underestimate of the risk of death, the Our World in Data team explained. It can be an overestimate when the untested sick don't make it into the official figures. Alternatively, it can be an underestimate, because deaths lag behind infections. The death rate will rise if the number of newly reported cases falls but people continue to die. Dr. Mike Tildesley, associate professor in the Department of Life Sciences at the University of Warwick, told Newsweek it is "crucial" to increase testing capacity and establish how many people have been infected and not sought hospital treatment to get a more accurate picture of the true death rate. In the meantime, death rates will continue to vary country by country and an overall average will be hard to pinpoint, suggested Strathdee. Current rough estimates of the case fatality rate range from 1 to 7 percent, she said, with the true figure "probably between the two." Germany, meanwhile, has been singled out as an apparent anomaly due to its relatively low death rate of 3.4 percent, versus 15.6 percent in Belgium. "In Germany, significant testing was carried out early on in the country's epidemic, which meant that more people were detected, many of whom only had mild symptoms. This testing regime resulted in the country reporting a much lower death rate than other countries in Europe," said Tildesley. So as screenings expands in countries later to rolling them out, like the U.S. and the U.K., people with mild or asymptomatic infections will be diagnosed, and "that will drive the death rate down," said Strathdee. "That's entirely expected," she said, adding: "It doesn't mean scientists or policymakers were wrong." The documentation of the deaths themselves is another piece of the puzzle lost to a lack of testing. When there are not enough kits to go around to test the living "health providers are less likely to order a test for a corpse to see what they died from," said Strathdee. "In some cases, patients are dying at home, or at a nursing home or prison without ever being diagnosed, and those cases may be missed. This can happen in cases where someone progresses to acute respiratory distress very quickly without other symptoms."

And with healthcare workers "all hands on deck" dealing with patients at this stage in the pandemic, said Strathdee, "paperwork recording causes of death, especially secondary causes of death, can get lost in the shuffle," Strathdee continued. "Someone may have died of a heart attack which is recorded as the primary cause of death, but the underlying cause of it may have been COVID-19, and that doesn't get recorded. Reporting is particularly challenging in the Global South where basic health infrastructure is lacking and there are so few doctors," she said. Dr. Sally S. Aiken, a working medical examiner and 2020 President of the National Association of Medical Examiners, told Newsweek it requires medical judgement to decide whether a person with an underlying condition died because of that or COVID-19. But she said "it is probably a rare case that is being attributed to COVID-19, that was truly caused solely by an underlying health problem. "Most medical examiners and coroners are much more concerned about under-reporting of COVID-19 deaths, because of a lack of test kits, or because people that die at home are not being tested, or false-negative tests," she said. Compounding all this is our limited understanding of a virus which humans have been aware of for just around 100 days. We are learning that it attacks many parts of the body, not just the respiratory and cardiovascular systems, said Strathdee, so when a person presents with unusual symptoms their coronavirus infection may be missed. But all this doesn't mean that trying to get a grip on how deadly the virus is is somehow impossible, futile, or that figures indicating the disease can be severe should be dismissed. According to Tildesley it is, for instance, important for to be able to characterize death rates by age, and for those with underlying health conditions. "This enables us to understand which individuals may be at the highest risk as a result of the ongoing pandemic and allow us to put in measures to protect these vulnerable members of society," he said. One study on over 44, 672 confirmed COVID-19 patients by the Chinese Center for Disease Control and Prevention published in the journal JAMA put the case fatality rate at 2.3 percent, rising to 8 percent in those aged 70 to 79-years-old, and 14.8 percent in the over-80s. In critically ill patients, the death rate was as high as 49 percent, on average. Broken down by underlying conditions, the risk was 10.5 percent for those with cardiovascular disease, 7.3 percent for diabetes patients, 6.3 percent for those with chronic respiratory disease, 6 percent in hypertension patients, and 5.6 percent for those with cancer. A separate study published in the JAMA on 5,700 patients with COVID-19 in the New York City area put the mortality rate 88 percent for those with cases so severe they need a ventilator. A person's ethnicity can also play a part, as reflected in a recent CDC report concluding current data suggests "a disproportionate burden of illness and death among racial and ethnic minority groups" for COVID-19. "Health differences between racial and ethnic groups are often due to economic and social conditions that are more common among some racial and ethnic minorities than whites. In public health emergencies, these conditions can also isolate people from the resources they need to prepare for and respond to outbreaks," the CDC noted. In the midst of an unprecedented crisis when many of us seek a concrete figure or statistic, like a death rate, to give a sense of context and to anchor our response to, all these figures can feel overwhelming. Fielder said: "We will really only get a fully accurate view of the death and recovery rate once the pandemic is declared as over and even then, there will be cases that have been missed due to the nature of reporting. "In the meantime," he suggested, "the best advice we can all follow globally is to stay at home, save lives and protect your health service."