The Basic Reproduction Number (R0) vs Effective Reproduction Number (Rt)

The Basic Reproduction Number or the R0 (R-nought) is often used by scientists as an indicator for the contagiousness or transmissibility of an infectious disease. However the R0 does not represent the actual reproduction number in a country as the actual reproduction number can be influenced by measures taken in a country (lockdown, mask usage, social distancing, etc.) or other circumstances (e.g. climate / weather)

To get an idea of the current contagiousness or transmissibility in a country or area, the Effective Reproduction Number (or Rt) is used. This number represents how many new cases one single person is to cause on average. When a R-value is above 1 it means that the outbreak is expected to grow, while a R-value below 1 indicates that the virus eventually will stop spreading.

In recent weeks many countries are reporting their current R-value on official government websites and/or COVID-19 government reports. Below an impression of the current R-values in Europe according to national authorities.

France

On July 9 a new week report was released by the Santé Publique France. Compared to two weeks ago the R-value has gone up from 0.92 to 1.05 for mainland France. The full list of R-values in France per region is shown below. (Source: Santé Publique France)

Luxembourg

In the Grand Duchy of Luxembourg a massive COVID-19 testing operation is taking place, with Luxembourg reporting SIX times as many tests per capita in recent weeks than USA, while USA is one of the countries with the highest testing activity! Because of this, Luxembourg is a very interesting country to monitor. The ministry of health of Luxembourg currently has the reproduction rate on 1.09. (Source: MOH Luxembourg)

Austria

The Austrian R-values are published by the public health authority: Agentur für Gesundheit und Ernährungssicherheit (AGES). In the latest report by AGES, the effective reproduction number is estimated at 1.29. (Source: AGES)

Germany

Encouraging signs are coming from Germany! After a spike in the R-value in June, Germany's R-value has been moving downwards in recent weeks. The Robert Kock Institute currently has the Reproduktionszahl at 0.90 (7-day R-value) for Germany. (Source: RKI)

Belgium

Unfortunately the Belgian authorities have stopped publishing the week reports, which included the R-value last two weeks. According to Belgian news reports however, Sciensano still has the reproduction number for Belgium at 0.87. (Source: Sciensano)

Spain

Two weeks ago I reported and published a screenshot of the Spanish chart with the R-value being at 0.86, but looking back to the data now, the R-value for 21 June has now been revised to 1.19! Because of the data revision before, because of the big drop at the end in the chart below and because of the high number of new cases in Spain in recent days, I'm going to predict the R-value for Spain for the most recent day (July 5) is going to be revised to be above 1. For now it officially stands at 0.89. (Source: Instituto de Salud Carlos III)

The Netherlands

The Netherlands reports the R-value with a lot of delay, but the latest estimate has the reproduction number at 1.06. (Source: RIVM)

Norway

Just like previous weeks, Norway does not give a number as an estimate, but describes it in text. Although the chart looks quite different, the latest week report explains that the amount of new detected cases is more or less flat, and that's why the Norwegian health institute estimates the R-value to be "close to 1, most probably below 1". (Source: Folkehelseinstituttet)

Do you know of more European governments who publish a Rt-value? Share it with us by sending an e-mail or Twitter message!