Is COVID-19 Peaking in Ontario?

It is now Day 85 of the start of the Covid-19 pandemic in Ontario as dated from the first case on January 25th of 2020.  There are signs of the epidemic peaking in parts of Canada like British Columbia and Saskatchewan along with discussion of the gradual reopening of activity in measured and methodical ways.  In Ontario,  as of Saturday morning the 18th of April, there have been 10,010 confirmed cases of COVID-19 and a total of 514 deaths.  The number of new cases reported today was 485,  down from 564 the previous day and 514 the day before that.  There has been some talk in Ontario also that the pandemic may be slowing and that there is some cause for cautious optimism.  Indeed, the province is expected to release new modelling numbers on Monday that some have hinted may show some support for optimism.



Well, in anticipation of that, here is my go at the numbers to date using STATA and a simple data smoothing regression technique known as LOWESS.  Figure 1 plots the total number of cases since Day 1(January 25th) when there was the first case to the present with the red line as the smoothed curve.  Needless to say, this figure does not look particularly reassuring but it is the total cumulative number of confirmed cases and the more appropriate graph in order to judge growth rates in the total case figure is Figure 2 which presents the log of total confirmed cases.  Here the evidence still shows an increase but somewhere around Day 70 - that is around April 3rd - there does seem to be a change in the growth rate and the curve trends upwards less steeply.  This is a bit of good news.



Figure 3 is yet another go at the numbers, this time a plot of the number of new confirmed cases per day again with a regression smooth.  The number of new cases per day begin to soar circa Day 50 which is March 14th but again note that the trend in new cases per day - as visualized by the LOWESS smooth - goes up at a lower rate again circa the April 3rd point.



However, the best news of all comes from looking at the growth of cases per day in terms of daily percentage growth rates in total confirmed  cases.  Figure 4 presents this data with the accompanying LOWESS smooth.  One can discount the far left of the diagram as this is the start of the pandemic with few cases and therefore some very large growth rates when the number of cases double.  The data smooth line basically shows the increase in growth rates picking up steam after Day 20 - which would be the 13th of February though the actual data starts picking that up closer to Day 30 which is February 23rd.  The  daily percent growth peaks a bit before Day 60 - March 24th - and then starts to slowly come down.  Growth has been under 8 percent since April 11th and just fell below 6 percent in today's release coming in at 5.1 percent.



So, despite my limited knowledge (borrowing from Star Trek, "I'm an economist Jim, not an epidemiologist!"), I would hazard to guess that the infection numbers today reflect what was going on about ten days ago. This gets further complicated by the fact that we are running more tests today than we were ten days ago and indeed a month ago.  Nevertheless, if we are testing more and the total number of new cases is stable but not soaring and the percentage growth rates seem to coming down, then yes we may be on the verge of bending the curve downwards and getting the pandemic under control in this province.  Assuming over the last 10 days, we have all continued physical distancing and taking precautions and the number of tests is maintained at current levels or increased, then the growth rates this week should come in about 5 percent at the start of the week and then head down towards 4 percent by Friday.  Let us hope.