Expectation management - Confirmed cases
The confirmed cases figure yesterday was 51,608. My fancy spreadsheet that aligns total positive tests with other countries with says that today we can expect total confirmed cases to be between a low of 56,100 (if we follow Germany's trajectory at this point) and a high of 59,300 (if we follow the trajectory of Spain).
Our European brothers all stepped up very tightly in this range, it seems reasonable that we will too.
We now have the eighth most confirmed cases in the world, the other top countries were USA (64,600 confirmed cases at this point) and Iran (54,200 confirmed cases), we are unlikely to follow either of their trajectories.
The daily increase for the UK over the past week have been between 7.9% and 17.2%, averaging 12.9%, which would be a total of 58,260 confirmed cases announced today.
Its arguable there's a downwards trend or a slowing of the rate of increase which might point to a percentage increase of 11.8% today, which would be 57,700 confirmed cases.
If we're really staring hard at the daily increase, and assume its rising in a linear manner then it might be an increase of 5,150, to a total of 56,760 which would be an 10% increase.
Yesterday there were 3,802 new confirmed cases announced, although we have come to expect a Monday dip, this was far below the usual expected dip. If there was the same increase today the total would be 55,410. If today's figure is below this then we can say that the rate is slowing, although some might say that you need to see a three day trend or a five day trend or seven days
Yesterday's figure for total UK deaths was 5,373.
There are only four other countries with comparable deaths to the UK, they stepped from 5,373 cases to a low of 5,970 deaths (Italy) and a high of 6,520 (Spain).
We can no longer compare our figures with China or Iran, their trajectories are lower than ours (based on official numbers).
By percentage, the UK figure has been growing by an average of 21.3% each day, which points to 6,517 today.
Yesterday there were 441 new deaths added to the total, if there was the same today it would be 5,814, if the announced figure is less than this then it is a genuine three day slowing trend. If we make assumptions based on the 'Monday dip' then anything under 5,990 would be in line with a slowing trend.
In seven days time we'll likely have between 74,000 and 96,000 confirmed cases. Deaths will be in the range of 9,000 to 10,800. Hopefully the outbreak will have peaked by this point, and its possible the UK won't reach 1,000 deaths per day.
Predicting one day ahead is easy, growth rates don't change much from one day to the next, but with exponential growth guessing further ahead is a mug's game.
Can I make a brief point about Confirmed Cases. I'm not an epidemiologist, but I'm halfway through this excellent free online course from the John Hopkins university about Fighting COVID-19 with Epidemiology.
One of the first lessons is about how in outbreaks such as this cases are divided into three categories, Suspected, Probable and Confirmed. In no way is the Confirmed Cases figure a comprehensive figure for the totality of the outbreak, it is merely some metric confirmed by a lab that can be studied to see if different policies and actions have made any difference to the outbreak.
The Suspected figure is difficult to count and estimate. Early on in the outbreak something like 95% of Suspected cases were tested and came up negative. Most people suspected of having COVID19 didn't have it.
So rather than argue that the Confirmed Cases figure is unrepresentative, we can just accept it as it stands and see if the lock-down has affected it, or if Monday's affect it.