How many people has the coronavirus killed? | Epidemiology - Nature

Researchers are struggling to tally mortality statistics as the pandemic rages. Here’s how they gauge the true toll of the coronavirus outbreak, writes Giuliana Viglione, News Intern at Nature.

Mourners attend a burial in Manaus, Brazil. The country has so far recorded more than 110,000 deaths from COVID-19.
Photo: Michael Dantas/AFP/Getty

At the beginning of March, Andrew Noymer felt a familiar twinge of doubt. He was watching countries across Europe and North America begin to record their first deaths from COVID-19, and he knew there could be problems with the data. Even in a normal winter, some deaths caused by influenza get misclassified as pneumonia. If that can happen with a well-known disease, there were bound to be deaths from COVID-19 going unreported, thought Noymer, a demographer at the University of California, Irvine. “I just remember thinking, ‘this is going to be really difficult to explain to people’,” he recalls.

And in March and April, when national statistics offices began to release tallies of the number of deaths, it confirmed his suspicions: the pandemic was killing a lot more people than the COVID-19 figures alone would suggest.

In times of upheaval — wars, natural disasters, outbreaks of disease — researchers need to tally deaths rapidly, and usually turn to a blunt but reliable metric: excess mortality. It’s a comparison of expected deaths with ones that actually happened, and, to many scientists, it’s the most robust way to gauge the impact of the pandemic. It can help epidemiologists to draw comparisons between countries, and, because it can be calculated quickly, it can identify COVID-19 hotspots that would otherwise have gone undetected...  

Blunt tool
When deaths began creeping up in Europe, Lasse Vestergaard was one of the first to notice. Vestergaard, an epidemiologist at the Statens Serum Institut in Copenhagen, leads the European Mortality Monitoring Project (EuroMOMO), which aggregates weekly all-cause death data from 24 European countries or regions. Between March and April, EuroMOMO’s tracker showed tens of thousands more deaths than expected — about 25% higher than the official COVID-19 deaths figure. Infections were slipping under the radar because of a lack of testing, and because different countries counted deaths in different ways — excluding deaths occurring in care homes, for instance. It was nearly impossible to get a true sense of how countries were faring...

Demographers will probably never know the pandemic’s final toll with certainty, Noymer says. “You don’t get to scratch off the lottery ticket and find out the actual values underneath the grey plastic coating.” Once the pandemic subsides, disentangling the three types of death — and determining how many would have occurred in the absence of the virus — will be a process that will take months or even years. “We haven’t even settled on how many people died in the 1918 flu,” he says. “And we’ve had 100 years to sort out the numbers.”
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Additional resources
doi: 10.1038/d41586-020-02497-w

Source: Nature