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Excess mortality from the Coronavirus pandemic (COVID-19)

What is ‘excess mortality’?

Excess mortality is a term used in epidemiology and public health to define the number of deaths which occurred in a given crisis above and beyond what we would have expected to see under ‘normal’ conditions.1 We have previously written about excess mortality in the context of the death rates of young girls and in famines.

Here we are discussing it in the context of the coronavirus pandemic (COVID-19).

The World Health Organization define ‘excess mortality’ as:

“Mortality above what would be expected based on the non-crisis mortality rate in the population of interest. Excess mortality is thus mortality that is attributable to the crisis conditions. It can be expressed as a rate (the difference between observed and non-crisis mortality rates), or as a total number of excess deaths.”

To calculate ‘excess mortality’ in a given period we would look at the number of people who had died over this period, and compare it to the number we would have expected to have died. In other words, it is calculated as:

How do we know the baseline? How many people would we expect to die under ‘normal circumstances’?

Knowing the number of deaths during a period of the pandemic is not enough. To calculate excess deaths we still need to know how many people we would have expected to have died if the pandemic had no occurred. To do this it is common to compare the number of deaths during a period of the pandemic with the average number of deaths during the same period in previous years.

In the absence of crises, there is often only small variability in the number of people who die year-to-year. By looking at death tolls in previous years we can understand the baseline of how many people we would expect to have died without the pandemic.

As an example, to calculate the number of excess deaths in a given population in May: we could look at the total number of deaths observed in May this year, and subtract the average number of deaths in May in the previous 5 years.

Why is it important to look at excess mortality?

In our work on the Coronavirus pandemic we visualize the data on the reported number of deaths from COVID-19 for all countries. We update this data daily based on figures published by the European Centre for Disease Prevention and Control (ECDC).

But these figures – as reported by governments and national health ministries – are the number of confirmed deaths due to COVID-19. The number of confirmed COVID-19 deaths may differ from the total death toll from the pandemic for several reasons:

  • some (but not all) countries only report COVID-19 deaths which occur in hospitals – people that die from the disease at home may not be recorded;
  • some countries only report deaths for which a COVID-19 test has confirmed that a patient was infected with the virus – untested individuals may not be included;
  • death reporting systems may be insufficient to accurately measure mortality – this is particularly true in poorer countries;
  • the pandemic may result in increased deaths from other causes for a number of reasons including weakened healthcare systems; fewer people seeking treatment for other health risks; less available funding and treatment for other diseases (e.g. HIV/AIDS, malaria, tuberculosis);
  • the pandemic may result in fewer deaths from other causes – for example, the mobility restrictions during the pandemic might lead to fewer deaths from road accidents.

This list makes clear that the two statistics – confirmed deaths due to COVID19 and excess mortality – are giving a perspective on different questions. The confirmed deaths often undercount the total death toll, but in contrast to excess mortality they contain information about the cause of death. The excess mortality includes not only those who have died from COVID19, but also those from other causes. When during the studied period fewer people have died from other causes (such as road accidents) the excess mortality statistics might suggest a death toll from COVID19 that is lower than the actual total. This means both metrics are needed to understand the death toll of the pandemic.

Excess mortality statistics will only be available for a small number of countries

Excess mortality is unfortunately available for very few countries, and because the required data from previous years is lacking this will continue to be the case. When the goal is to monitor a global pandemic then this is a major limitation of this metric.

Excess mortality can only be calculated on the basis of accurate, high-frequency data on mortality from previous years. But few countries have statistical agencies that have the capacity and infrastructure to report the number of people that died in a given month, week or even day-to-day. For most low and middle-income countries, such data is not available for the last years.

As we see from the available excess mortality estimates – all listed below – this data is most often only available for richer countries that can afford high-quality data reporting systems.

Researchers can draw on some other sources to estimate excess mortality – such as funeral or burial records – or on data from subnational regions of poorer countries (often the capital) and in many cases no information at all can be obtained.

Publicly available data on excess mortality

International organizations are not publishing an international database on excess mortality

Unlike statistics on confirmed COVID-19 deaths – for which several organizations such as the WHO, ECDC and Johns Hopkins University are collating data for all countries – there is no single source of data on excess mortality.

This is a major problem for policymakers, researchers, and the general public that has a need to understand the ongoing pandemic.

Several media publications and regional data sources are publishing public databases

Several media publications and regional agencies have began publishing excess death data for some countries.

  • The Economist published the first database on excess mortality on GitHub.
  • The New York Times also publishes its dataset on excess mortality on GitHub.
  • Eurostat publishes downloadable data for European countries on its website.
  • Human Mortality Database publishes downloadable data for a number of countries on its website.

Our World in Data wants to build a public database on excess mortality, but we do not have the capacity currently

We at Our World in Data would want to build a publicly available database on excess mortality. Like all our work we would make it publicly available for others. This is absolutely key for any data work because only then can it can be scrutinized and checked by colleagues. It is also the morally required as it would be key information in the global effort of fighting this pandemic.

Unfortunately however we are a very small team and currently do not have the capacity to build such a database. (Our research team is currently mostly concerned with building a publicly available and widely used database on testing for COVID-19.)

Publications that are tracking excess mortality

The Economist

What is included in this data?
  • Visualization types: interactive
  • Countries: European countries only
  • Cities: a few cities covered, including Lombard, New York, and Istanbul
  • Age breakdowns: European data broken down by age group

See The Economists’ work on excess mortality.
It publishes this database online on GitHub.

Financial Times

What is included in this data?
  • Visualization types: static
  • Countries: more than ten countries; many across Europe, the US, Israel, and South Africa.
  • Cities: ten cities covered, in both high- and lower-income countries.
  • Age breakdowns: not included

See the Financial Times’ work on excess mortality.

EUROMOMO

What is included in this data?
  • Visualization types: interactive
  • Countries: European countries only
  • Cities: Not covered
  • Age breakdowns: available by age group

See EUROMOMO’s work on excess mortality.

New York Times

What is included in this data?
  • Visualization types: static
  • Countries: more than ten countries; many across Europe, the US, and Ecuador.
  • Cities: a few cities covered, including Jakarta, New York, and Istanbul
  • Age breakdowns: not included

See the New York Times’ work on excess mortality.
It publishes this database online on GitHub.