We May Be Underestimating the Coronavirus Death Toll
Many people believe we're under-counting the Covid-19 infection rate, but Italian data suggest we may be getting the death numbers wrong too.
The Covid-19 epidemic is a fight with an invisible enemy. What’s also worrying is that we just don’t know how bad the disease really is.
Many people wonder whether we’re overestimating its deadliness, since countries find it impossible to test those with few or no symptoms. The case fatality rate is the ratio of coronavirus deaths to the number of infected patients. If we underestimate the latter, the detected fatality rate will look much higher than the real one. That’s why there’s such huge interest in scientific models that suggest the overall infection rate is far in excess of the official numbers. If that were true, the mortality rate across the population would fall to less worrying levels.
However, Italy’s experience shows that countries may also be underestimating the other side of the ratio: the death toll. As hospitals become overcrowded, patients are being asked to stay at home until they display the most serious symptoms. Many will die in their houses or nursing homes and may not even be counted as Covid-19 cases unless they’re tested post-mortem.
Last week, two researchers from northern Italy made this point forcefully when looking at Nembro, a small town near Bergamo that has been very severely hit by the outbreak. Writing in Italian newspaper Corriere della Sera they found there had been 158 deaths in the town in 2020 so far, as opposed to 35 on average in the previous five years. They noted that Nembro had only counted 31 deaths from Covid-19, which looks like an underestimate.
In other towns nearby, including Bergamo itself, the trend seemed identical. The researchers made the point that the only reliable indicator in the end will be “excess deaths” — namely, how many more people have died in total compared to a “normal” year.
Deaths in Bergamo The number of deceased people in March in one of Italy's worst-hit cities Source: Comune di Bergamo, L'Eco di Bergamo Note: 2020 is as of March 26.
The statistical advantage of “excess deaths” is that they give you a fuller picture of the human cost of the pandemic. The number of people who die of Covid-19 is a significant part, but not all of it. There will also be people who suffer from other illnesses and who aren’t treated properly because hospitals are overcrowded, intensive care units full and ambulances take longer to arrive. Conversely, there will also be fewer deaths from, say, road accidents, because of the draconian restrictions some countries have chosen to impose. All of this will be captured in this one indicator.
There are signs that excess deaths are climbing in Italy, not just locally but nationally too. Italy monitors the number of deaths of those older than 65 in 19 large cities, including Milan and Rome. In the week between March 8 and March 14, this figure (scaled by the total number of residents) was significantly higher than in the past for all the groups above 65, and especially for those between 75 and 84.
And that week was still far from the peak of the epidemic, which Italy may only be approaching now. Some cities, including Bergamo, aren’t included in this survey. The human cost of the crisis will become inevitably larger as statisticians collect ever more reliable data.
Of course, this is only one side of the story. There are “hidden deaths” but there are also “hidden carriers,” making the fatality rate very hard to estimate. It’s reasonable to believe that Covid-19 is less lethal than the crude statistics suggest.
At the moment, Italy has about 12,500 counted deceased, out of slightly more than 105,000 confirmed infections. The fatality rate stands at 11.7%. By contrast, Germany’s number of deaths can still be counted in the hundreds, meaning its mortality rate is 1%. The global estimate from the World Health Organization is 3.4%, and even that is probably an exaggeration.
However, absolute figures matter here too. That more people survive doesn’t subtract from the tragedy of those who die — especially if the spike in deaths in Nembro is representative of what’s happening elsewhere. If Italy is any guide, other countries should not underestimate the human toll of Covid-19.
April 1, 2020, 9:00 AM GMT+3