Mortality lower than normal in week 20

The estimate for week 20 has been based on the number of death certificates CBS has received for that week up to and including Wednesday 20 May. Expected mortality has been estimated on the basis of mortality as recorded over the previous weeks, adjusted for seasonal effects. Had there not been a COVID-19 pandemic, week 20 would have an estimated 3,046 deaths.
Up to and including week 10 (ending 8 March) of this year, average mortality stood at 3,134 per week. It subsequently rose to reach its highest level in week 14 with 5,079 deaths.

Undermortality in week 20

It is a commonly known fact that periods of elevated mortality are often followed by periods of low mortality. This was also the case in 2018, when the elevated mortality during the influenza epidemic was followed by approximately six weeks of lower mortality.
However, the low mortality level in week 20 does not mean that there were no deaths related to COVID-19. In week 20, the number of deaths from COVID-19 as reported to RIVM (as at Thursday, 21 May 2020) stood at 159. The final number may turn out even higher, as not all COVID-19 patients are tested.

Lower mortality among over-80s and women in particular

Overall mortality has declined in all age groups as of week 14. In week 20, mortality was at a slightly lower level than what would normally be expected for this time of year. Mortality was even 9 percent lower than usual among people under the age of 80.

The decline set in as of week 14 for men and as of week 15 for women. No further decline was recorded among men in week 20; the drop did continue among the female population. Among men, week 20 mortality was 3 percent below the expected level, against 11 percent among women.

Elevated mortality since the start of the COVID-19 pandemic

The increase in mortality coincides with the beginning of the epidemic in the Netherlands. The first confirmed COVID-19 patient in the Netherlands was reported on 27 February 2020. The first death involving COVID-19 was reported on 6 March 2020. The COVID-19 outbreak was declared a pandemic by the World Health Organization (WHO) on 11 March 2020.

Data sources for CBS and RIVM

CBS receives mortality data on a daily basis from municipal registers. This is before it receives any information on the causes of these deaths. CBS receives such information by way of the death cause certificates which are completed by the physician who attended the deceased. The publication of data from death cause certificates is normally scheduled for Q3 2020, but CBS will make every effort to release this information at an earlier stage.
RIVM receives data on confirmed COVID-19 deaths from municipal health services (GGD) around the country on a daily basis. Since not all COVID-19 patients are tested, the actual number of COVID-19-related deaths in the Netherlands is expected to turn out higher. A more complete picture emerges by looking at the total weekly number of deaths as based on the data received by CBS, regardless of the cause of death.

Estimates based on death certificates received so far

In general, some time elapses between the actual date of death and the moment when this data reaches CBS. Death certificates are collected weekly on Thursdays. Usually, mortality data collected on Thursday include slightly over 80 percent of all deaths over the previous week. This information provides an indication of the number of deaths that can be expected for that week.
Based on the data obtained over weeks 12 through 19, death certificates are currently being received sooner than usual (as the number of certificates that was received after one week turned out to cover 85 percent of all deaths) with the exception of weeks with public holidays. The estimate for week 20 is based on the assumption that for this week as well, 85 percent has been received. As the percentage is uncertain, the actual number of deaths in week 20 may be higher or lower as a result.