The displayed time-series can be downloaded in .csv format here. This time-series is displaying our estimate of the effective reproduction number "Reff", based on growth data since the start of the epidemic. The number can be thought of as the expected number of infections directly generated by one additional infection. We estimate that the basic reproduction number (or "R") without any mitigation in most countries is likely somewhere between 2 and 5. Current values reflect all mitigation measures taken, and also that the fraction of susceptible individuals in the population is gradually decreasing.

The basic interpretation of this number is as follows

  • If R is below 1, the epidemic is shrinking.
  • If R is around and slightly above 1, the epidemic could be either shrinking or growing, but slowly.
  • If R is larger than 2 the the mitigation is insufficient to keep the epidemic under control, and the growth is rapid.