Reproduction number

Please note: The reproduction number is no longer updated.

Because few COVID-19 patients have been admitted to intensive care and nursing wards of hospitals for a long time, it is no longer possible to calculate a reliable reproduction number. The latest value is from July 11, 2023 and will no longer be updated.

Where do the numbers come from?

The National Institute for Public Health and the Environment (RIVM) supplies open data on the reproduction number. The reproduction number (R) is not an exact value but a reliable calculation.

• Read the open data set on the reproduction number on the website of the RIVM
• Read the description of the data set on the reproduction number on the website of the RIVM

How are the numbers calculated?

To calculate the reproduction number R, the number of cases of COVID-19 that increases over time is needed. For this, RIVM uses the number of reported COVID-19 cases per day in the Netherlands. In addition, the time between the first day of illness of a COVID-19 patient and the first day of illness of his or her infector is also examined. Based on the data from the Netherlands, we know that the average time is 4 days. There is an existing method for estimating the reproduction number for this.

The figures on hospital admissions are always a bit behind, because it is not yet clear on the first day of illness of a patient whether that patient will be admitted to hospital. Sometimes reports are passed on or changed a little later. RIVM takes this reporting delay into account. The estimates of the R longer than 14 days ago are reliable. If the R is based on data from less than 14 days ago, the uncertainties are greater. We therefore do not show 'Today's 'R', because the uncertainties are too great for that.

The data used for the calculation of R:

Data from the National Intensive Care Evaluation (NICE). These are figures about the number of hospital admissions in the Netherlands and the number of admissions to intensive care.

Data from the GGD (Municipal Health Service). They put information about new patients with COVID-19 in the system OSIRIS (information system) information system . They indicate the number of new patients, their first day of illness, the possible source of infection and the number of people admitted to hospital. All data is sent to RIVM via OSIRIS. RIVM manages this system and is working on making this data accessible.

• Read the explanation of how the reproduction number is calculated on the website of the RIVM

The most up-to-date value of R provided on the coronavirus dashboard at any given time is always from at least two weeks ago. Calculations of R using data from less than 14 days ago could provide an indication of what the definitive value may be, but are not reliable predictors. The more recent the day, the less reliable the figure is since not all the data for that day is available yet.

Adjustments

From 15 March 2023, the reproduction number has been calculated again based on COVID-19 hospital admissions according to the NICE hospital registration.

From 13 June 2020 to 14 March 2023, the reproduction number was calculated on the basis of COVID-19 reports to the GGD. However, the number of reports is strongly determined by the test policy, and is less suitable as a basis for calculating the reproduction number due to the adjusted test policy and the closure of the GGD test lanes as of 17 March 2023.

Until 12 June 2020, the reproduction number was also calculated on the basis of hospital admissions, but then as reported to the GGD.