Over the next few weeks, people in Britain will be anxiously be looking for ‘the peak’. This short thread is to explain what ‘the peak’ is and what signs of hope we should be looking for.

There are actually several peaks expected to occur at different times. The earliest sign of a slow-down will be a peak in the number of daily cases divided by the total cases on the previous day. This number is a constant for a true exponential growth.

In Italy, this parameter might have peaked on the 7th of March at about 27%, which means 27 new cases on March 7th for every 100 total cases on March 6th. It now stands at about 13%. There are a lot of ups and downs in this value, so don’t hope too much if you see a drop.

Next, one should expect a peak in the daily change in total cases (or in the number of active cases, which is lower and may peak slightly earlier). This parameter may be peaking in Italy this week: there were 3233 new cases yesterday vs 3590 on Sunday.

Next, we will hopefully see a peak in the number of active cases - this may take another week or more. Finally, the number of daily deaths will peak.

A good collection of graphs on Italy is here https://lab24.ilsole24ore.com/coronavirus/  Final word of advice: don’t get fooled by daily fluctuations: it takes 3-4 days to consolidate a trend.