A very interesting article I stumbled across today:
https://science.sciencemag.org/content/early/2020/05/14/science.abb9789Some key findings:
- Before government interventions and voluntary social distancing by the people, the effective growth rate (new infections minus recoveries) of Covid-19 in Germany was about 30% per day.
- Cancelling mass events, coupled with the onset of voluntary behavioral changes which have started around that time according to movement data from phone companies ( https://www.covid-19-mobility.org/current-mobility/ ), brought this down to 12%. (Note that a daily growth by 12% is still catastrophic!)
- Closing schools, childcare centers and most shops, coupled with further voluntary reduction in mobility, brought the effective growth rate down from 12% to 2%. This is still technically exponential growth, but it would take 35 days to double the number of active cases. At this rate, it would take several months until the situation gets out of hand.
- The official shutdown (contact ban, closing all non-essential shores) brought the effective growth rate down from +2% to -3%.
- The average number of days an infected person is infectious was found to be 8.6 days during the initial phase, slightly lower later on.
- Based on the estimated recovery rate (inverse of the number of days an infected person is infectious), this corresponds to R_0 = 0.76.
- The average reporting delay was estimated to be 11.4 days.
One important caution follows at the end of the discussion section:
Quote
At present, estimates of effective growth rates dropped to −3% and thereby remain close to zero – the watershed between exponential growth or decay. Together with the delay of approximately two weeks between infection and case report this warrants caution in lifting restrictions for two reasons. First, lifting restrictions too much will quickly lead to renewed exponential growth and second, we would be effectively blind to this worsened situation for nearly two weeks in which its transmission will be uninhibited. This may result in a growth in case numbers beyond the level that the health system can cope with, especially if active cases are not close to zero before lifting restrictions. Therefore, it is important to consider lifting restrictions only when the number of active cases are so low that a two-week increase will not pose a serious threat to healthcare infrastructure.
If any of you have methodological questions about the article, feel free to ask, I'll try my best to answer them. (This stuff is not my field of expertise though, but I'm probably better positioned to grasp it than most.)
This post was edited by Black XistenZ on May 23 2020 11:22pm