COVID-19 mortality

1. COVID-19 mortality

Background

COVID-19, a new disease

COVID-19 disease is caused by the SARS-CoV-2 virus. The most frequent symptoms are fever, cough, and shortness of breath. In 80% of cases, the infections are mild. The risk of developing a severe infection increases markedly with age and with underlying conditions such as heart, lung, or kidney disease, diabetes, immunosuppression, or an active malignant disease.

Case definitions
  • COVID-19 cases: According to ECDC [1], a COVID-19 case can be defined by laboratory criteria i.e. a positive molecular test, by diagnostic imaging criteria i.e. radiological evidence showing lesions compatible with COVID-19, or by clinical criteria i.e. a person with at least one of the following symptoms (without other clear causes) cough, fever, shortness of breath, or sudden onset of anosmia, ageusia or dysgeusia. ECDC has also defined some degree of confidence in the diagnosis, according to the diagnostic method [1] and has classified the cases into “confirmed”, “probable”, and “possible”.
  • COVID-19 deaths: the World Health Organization (WHO) states that “a death due to COVID-19 is defined for surveillance purposes as a death resulting from a clinically compatible illness, in a probable or confirmed COVID-19 case, unless there is a clear alternative cause of death that cannot be related to COVID disease (e.g. trauma)” [2], and ECDC later on also adopted these inclusion criteria [1]. Belgium has adopted a broader inclusion strategy for the surveillance of deaths, reporting also deaths in possible cases based on clinical symptoms. Deaths occurring in hospitals, long-term care facilities (LTCFs), and in the community were reported. The rationale for broadening the case-definition of a COVID-19 death was the low testing capacity during the first weeks of the epidemic, leading to a quasi-impossibility to get a lab-confirmed diagnosis for patients in LTCFs. As a result, monitoring only deaths in confirmed cases would have hidden the severity of the epidemic.
Surveillance of COVID-19 deaths

In pandemic times, almost real-time monitoring of mortality is essential. In Belgium, the cause-specific mortality registration through death certificates is a two-year process, which was not suitable for operational surveillance. For this reason, an ad-hoc registration in nearly real-time of COVID-19 mortality was set up in emergency. Deaths in hospitals are registered through the Hospital Surge Capacity survey managed by Sciensano. Deaths outside the hospital (in nursing homes, other institutions, at home, and other places) are notified to the regional authorities via specific tools. Sciensano is in charge of compiling the information from the different data sources. COVID-19 deaths can only be fully reported by place of deaths for data availability reason (place of residence was not available for hospital deaths until the 24/04). More information is available in a dedicated paper [10].

Indicators

The following indicators will be presented here:

  • The number of COVID-19 deaths in Belgium (source: COVID-19 mortality surveillance of Sciensano)
  • Crude mortality rate due to COVID-19 per million of inhabitants (source: COVID-19 mortality surveillance of Sciensano)
  • Crude mortality rate due to COVID-19 per million of inhabitants in selected countries for international comparisons (source: report of ULB-VUB [3], from ECDC original data [4])

There is an important limitation in the international comparability of these indicators. Because of important differences in death notification methods between countries [5], COVID-19 mortality comparisons are not well suited for international comparisons. Indeed, in Belgium, deaths in hospitals as well as outside the hospitals are counted, moreover, deaths of patients with a positive laboratory test, a suggestive chest CT scan, or clinical symptoms are notified as COVID-19 death, while many other countries were much more restrictive. Therefore, we shall complete figures of COVID-19 mortality rates with other indicators (see the section “all-cause and excess mortality”).

Presentation of the results

As the situation is continuously evolving, this page presents:   

  • The situation at the end of the first wave (10 March–21 June 2020) of the COVID-19 epidemic in Belgium.
  • For the ongoing situation, this page provides links to the different Sciensano epidemiological COVID-19 pages.

First wave (10 March–21 June 2020)

Belgium

The first COVID-19 death in Belgium occurred on March 10th, 2020.

On the 21st of June (extracted on the 2nd of October), 9585 deaths were notified in Belgium, representing a crude cumulative death rate of 834 per million inhabitants. The peak was observed on April 8 with 321 deaths.

More than half of the people were aged over 85 years old.

Number of deaths due to COVID-19 by date of death and by region of death until the 21 of June 2020, Belgium
Source: COVID-19 mortality database, Sciensano
  • Number of deaths
  • Mortality rates

Number of deaths due to COVID-19 by age group and gender until the 21 of June 2020, Belgium
Source: COVID-19 mortality database, Sciensano

Age-specific mortality rates due to COVID-19 (per million inhabitants) by gender until the 21 of June 2020, Belgium
Source: COVID-19 mortality database, Sciensano

 

Regional specificities

The regional differences in COVID-19 mortality rates during the first wave were moderated: the cumulative rates expressed per million inhabitants were respectively 1212 in Brussels, 922 in Wallonia, and 716 in Flanders. As the death rates are calculated by region of death, the slightly higher mortality rate (expressed by place of death) in Brussels can probably be partly explained by a higher concentration of hospitals in a region exclusively made up of a large city. Also, the high density of the population in urban zones enables the circulation of the virus.

 Ongoing situation

Since the data are in constant evolution, this sheet refers to the main webpages where values are updated everyday. Data can be consulted in several places and several forms:

  1. Dynamic dashboard
  2. Reports:
    1. Daily reports present the main indicators by region and their evolution. In the appendix, more detailed numbers and trends by province are available.
    2. Weekly reports with more detailed analyses were published during wave 1.
  3. Open data are available. Data for COVID-19 mortality contain the number of deaths aggregated by age groups, by sex, by date of death, and by region.
  4. Frequently asked questions are answered in a specific document.

International comparisons

Belgium has attracted attention internationally due to high COVID-19 related mortality. Belgium has indeed one of the highest cumulated death rate in Europe. However, due to the methodological limitations mentioned, those figures have to be interpreted with caution. Other indicators are best suited for cross-country comparison (see the section “all-cause and excess mortality”).

Cumulative mortality rate by COVID-19 (deaths per million), 15/02 to 29/06, selected countries
Source: ULB-VUB report on mortality [3], mortality data extracted from ECDC [4]

Epidemiological International data can be consulted on several platforms:

2. All-cause and excess mortality

Background

In the context of measuring the impact of the COVID-19 on the mortality, it has been recommended [3,6] to use the excess all-cause mortality to:

  • Assess the reporting of the COVID-19 mortality resulting from the ad-hoc surveillance system
  • Measure the global impact of the COVID-19 on the mortality burden
  • Allow international comparisons that are less biased than the COVID-19 mortality

Observed number of deaths (from all-cause): the number of deaths in Belgium is registered by the Belgian National Registry. This process is continuous and quite rapid, as more than 95% of the deaths are registered within 3 weeks. The information available through this dataflow does however not contain the cause of death, that will become available after 2 years. The information is transmitted to Sciensano for the detection of unusual mortality (Be-MOMO project) and to Statbel for the publication on their website and the calculation of basic vital statistics.

The excess mortality is defined as the number of observed deaths exceeding the expected number of death (baseline) for a given day. The number of expected deaths (baseline) can be calculated with different methods that can provide slightly different results.

  1. The Be-MOMO project (Belgian mortality monitoring) is a surveillance of all-cause mortality carried out by Sciensano on a weekly basis. The mortality monitoring model is a tool for rapid detection and quantification of unusual mortality (which might result from disease epidemics such as influenza or from extreme environmental conditions such as heat/cold waves or environmental pollution). A timely assessment of the impact of particular events on mortality may be useful to guide public health measures, e.g. vaccinations for influenza and the national heat action plan [7]. The model predicts the daily expected number of deaths along with a prediction interval, by modeling the past 5-year mortality data and past epidemic seasons and extreme environmental events (cold and heat waves, and air pollution). A daily observed number of deaths falling outside the prediction interval reveals statistically significant mortality deviance from the expected number. When the number of observed deaths exceeds the upper prediction limit there is a significant mortality excess for this day, allowing to visualize correlations between mortality deviance and those events [7,8]. The weekly updated figures of Be-MOMO can be found on Epistat.
  2. In 2020, in the context of the COVID-19 epidemic, other calculations have been made to obtain the excess mortality with slightly different methodologies [3,9]. The main differences with Be-MOMO are the use of different years as baseline, the absence of correction for unusual events in previous years, and the fact that they do not take into account a prediction interval.

In this report, we will use the following indicators and data sources:

For Belgium
  • Excess of all-cause mortality, expressed as a “P-score”: it is calculated as the number of excess deaths: (observed – expected)/expected *100
    • This excess is presented by week between the 10th of March and the start of June 2020. The average P-scores are presented for the following periods:
      • From week 13 to week 18, when the excess reaches the statistical significance
      • From week 11 (first COVID-19 death) to week 21 (no more excess mortality)
  • Comparison between the excess mortality and the COVID-19 deaths during the first wave.
For international comparisons

We will use selected international and regional comparisons from the mortality report of the ULB-VUB [3]. The researchers have selected some EU countries based on the relevance of the comparison with Belgium. The original data came from ECDC [4] and ONS-UK [9].

All-cause mortality and excess mortality

An excess mortality during the first wave of the COVID-19 epidemic was observed in Be-MOMO from week 12 of 2020 (starting on 16/3/2020) to week 19 (ending on 10/05/2020); this excess was statistically significant from week 13 (23/3) to week 18 (ending on 3/5), with a peak reaching 100% excess in week 15 (6/04). This is a good indicator of the global impact of the COVID-19 on mortality. However, a final toll of excess death can only be made by the end of the year, since the excess mortality period can be compensated by periods of under mortality.

The average excess during the period where it is was statistically significant (weeks 13 to 18) was 61%, with important age disparities: it reached 76% in people aged 85+, 62% in people aged 65-84, and 18% below 65 years. The average excess during the period from the first COVID-19 death to the end of the excess mortality period (weeks 11 to 21) was 37%.

Number of all-cause deaths by week, Belgium
Source: Be-MOMO [7] and COVID-19 mortality database, Sciensano
Covid mort EN

Comparison between excess mortality and COVID-19 mortality

During the first wave, an excellent correlation (91%) was found between all-cause mortality and COVID-19 mortality. This validated the inclusion criteria for COVID-19 related deaths [6].

Expected number of deaths and confidence intervals, observed number of deaths, and COVID-19 deaths until 22/06, Belgium
Source: Be-MOMO [7] and COVID-19 mortality database, Sciensano

 

Graph created by Mathias Leroy
 
More information

International comparisons

Due to the methodological issues mentioned before, the excess all-cause mortality during the first wave of the COVID-19 is a more suited indicator than the COVID-19 specific mortality for international comparison of the impact of the COVID-19. Using this indicator, the UK, Spain, and Italy have the highest mortality rates in the selection of countries.

Cumulative excess mortality rate (deaths per million), during the respective period of excess mortality of the countries, selected countries
Source: ULB-VUB report on mortality [3], mortality data extracted from ECDC [4]

References

  1. ECDC. Case definition for coronavirus disease 2019 (COVID-19), as of 29 May 2020. https://www.ecdc.europa.eu/en/covid-19/surveillance/case-definition
  2. WHO. International guidelines for certification and classification (coding) of COVID-19 as cause of death. WHO; 2020 Apr. Report No.: WHO/HQ/DDI/DNA/CAT.
  3. Lagasse R, Deboosere P. Évaluation épidémiologique de l’impact du Covid-19 en Belgique à la date du 15 juillet 2020. https://esp.ulb.be/fr/les-actus/l-esp-dans-les-medias/rapport-d-analyse-de-l-epidemie-covid-19-n-ii
  4. ECDC. Daily number of new reported cases of COVID-19 by country worldwide. https://www.ecdc.europa.eu/en/publications-data/download-todays-data-geographic-distribution-covid-19-cases-worldwide
  5. European Centre for Disease Prevention and Control (ECDC). Weekly surveillance report on COVID-19, Week 24, 2020. https://covid19-surveillance-report.ecdc.europa.eu/#4_severity
  6. Bustos Sierra N, Bossuyt N, Braeye T, Leroy M, Moyersoen I, Peeters I, et al. All-cause mortality supports the COVID-19 mortality Belgium: comparison with major fatal events of the last century. Submitted.
  7. Sciensano. Epistat – Belgian Mortality Monitoring (Be-MOMO). https://epistat.wiv-isp.be/momo/
  8. Cox B, Wuillaume F, Van Oyen H, Maes S. Monitoring of all-cause mortality in Belgium (Be-MOMO): a new and automated system for the early detection and quantification of the mortality impact of public health events. Int J Public Health. 2010 Aug 1;55(4):251–9.
  9. Campbell A, Morgan E. Comparisons of all-cause mortality between European countries and regions. Office for National Statistics; 2020. https://www.ons.gov.uk/peoplepopulationandcommunity/birthsdeathsandmarriages/deaths/articles/comparisonsofallcausemortalitybetweeneuropeancountriesandregions/januarytojune2020
  10. Renard F, Scohy A, Van der Heyden J, Peeters I, Dequeker S, Vandael E, et al. COVID-19 mortality surveillance: the Belgian experience. Submitted to Eurosurveillance