COVID-19 reproduction number

The reproduction number R gives the average number of people infected by one person with COVID-19. To estimate this reproduction number, we use the number of reported COVID-19 cases per day in the Netherlands. Because a COVID-19 case is transmitted with some delay in the reporting system, we correct the number of cases for this delay [1]. For a large part of the reported cases, the first day of disease is known. This information is used to estimate the first day of illness for the remaining cases. By showing the number of COVID-19 cases per date of first day of disease, it is immediately visible whether the number of infections is increasing, peaking or decreasing. For the calculation of the reproductive number, it is also necessary to know the length of time between the first day of disease of a COVID-19 case and the first day of illness of his or her more infected. This duration is on average 4 days, calculated on the basis of COVID-19 reports to the GGD. This information calculates the value of the reproduction number as described in Wallinga & Lipsitch 2007 [2]. Until 12 June, the reproduction number was calculated on the basis of COVID-19 hospitalisations. Estimates of the reproduction number R more recent than 14 days ago may be an indicator of the final value, but are not reliable as a predictor. The reliability of the estimate is reduced for more recent days, as reports for recent days have not yet been fully reported and the number of reports for future days cannot yet be known. Therefore, no point estimate of R is given over the last 14 days, but the upper and lower limits are given. [1] van de Kassteele J, Eilers PHC, Wallinga J. Nowcasting the Number of New Symptomatic Cases During Infectious Disease Outbreaks Using Constrained P-spline Smoothing. Epidemiology. 2019;30(5):737-745. doi:10.1097/EDE.0000000000001050. [2] Wallinga J, Lipsitch M. How generation intervals shape the relationship between growth rates and reproductive numbers. Proc Biol Sci. 2007;274(1609):599-604. doi:10.1098/rspb.2006.3754. Description of variables: version: Version number of the dataset. If the contents of the dataset are structurally modified (i.e. not the daily update or a correction at record level), the version number will be modified (+ 1) and also the corresponding metadata in RIVMdata (data.rivm.nl). Date: Date for which the reproduction number was estimated Rt_low: Lower bound 95 % confidence interval Rt_avg: Estimated number of reproductions Rt_up: Upper limit 95 % confidence interval population: patient population with value “Hosp” for hospitalised patients (t/m 12 June 2020) or “testpos” for test positive patients (after 12 June 2020) Please note: from Friday 5 March 2021, the open dates of the reproduction number will be published twice a week. On Tuesdays and Fridays, at 3.15 p.m. Changelog: Version 2 update (8 February 2022): In the calculation of the reproduction number, instead of the GGD notification date, the date of positive test result is now used.